Unit 4 - Stevens [Type the document title]

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Unit 4: Atomic Structure and the Periodic Table

Vocabulary:

Term Definition

Atom

Proton Sub-atomic particle with positive (+) charge; located in nucleus of atom;

determines identity of element

Neutron

Electron Sub-atomic particle with negative charge; much smaller than protons and

neutrons

Nucleus

Valence Electron Electron found in outermost shell of an atom; determines atoms chemical

properties

Atomic Number

Mass number

Atomic Mass Weighted average of masses of isotopes of each atom

Isotope Atom with same # of protons as other atoms of that element, but different #

of neutrons

Ion

Bohr Model Model used to visualize atomic structure

Lewis Dot Structure

pH scale

Acid

Base Compound which increases hydroxide ions (OH-) when dissolved in H2O

Gravitational Force Attraction of objects due to their masses and distance; weakest force

Electromagnetic

Force Force

Weak Nuclear Force

Strong Nuclear Force Holds the atomic nucleus together; Counteracts the electromagnetic force

Periodic Table e

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Group Vertical (up and down) column of periodic table; elements in group share

chemical properties (same # valence electrons)

Period

Metals

Non-metals usually gases or brittle solids at room temp; are poor conductors; to right of

stair step

Metalloids Have characteristics of metals and non-metals; make up stair step

Section 1: Atomic Structure

Key Ideas

• Know the structure of atoms

• Explain how sub-atomic particles are different in terms of mass, electrical charges, and location in

the atom

• Understand Hydrogen ion concentration in acids and bases, and how the pH scale measures acids

and bases

Vocab:

• Atom Valence Electron Ion

• Proton Atomic Number Bohr Model

• Neutron Mass Number Lewis Dot

• Electron Atomic Mass pH scale

• Nucleus Isotope Acid

Base

Watch video and answer:

How small are atoms? _______________________________________________________

If they are so small, how do we know they exist? __________________________________

__________________________________________________________________________

History of the Atom:

• For thousands of years, many scientists have been trying to figure out what makes up all matter? Of

course, its atoms. But what are they made of? What do they look like? How do they work?

• After many scientists contributions, and many experiments, we now have a __________________

____________________________________, that is supported by all previous evidence

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Progression of the Atomic model and History of the Atom Timeline:

Scientist Picture of Model Name Discovery

Billiard Ball Model

Plum Pudding Model The Electron

The Proton

Bohr Model

Electron Cloud Model Can not predict exactly

where an electron will

be; electrons have erratic

behavior

The Neutron

What are the building blocks of matter? __________________________________________

What is matter? _____________________________________________________________

What are atoms made of?

• Smallest possible unit into which matter can be divided, while still maintaining its properties.

• Made up of:

– _________________________________

– _________________________________

– _________________________________

• The solar system is commonly used as an analogy to describe the structure of an atom

Atoms are so small that:

• It would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum

foil from your kitchen.

• If you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3

cm in diameter – about the size of a ping-pong ball

• A human hair is about 1 million carbon atoms wide.

• A typical human cell contains roughly 1 trillion atoms.

• A speck of dust might contain 3x1012

(3 trillion) atoms.

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• It would take you around 500 years to count the number of atoms in a grain of salt.

Protons:

• _________________________________________________________________________________

• _________________________________________________________________________________

• _________________________________________________________________________________

• _________________________________________________________________________________

• Help identify the atom (could be considered an atom’s DNA)

Neutrons:

• _________________________________________________________________________________

• _________________________________________________________________________________

• _________________________________________________________________________________

• _________________________________________________________________________________

• Mass number – protons = neutrons

Electrons:

• Negatively charged particles

• Found outside the nucleus of the atom, in the electron orbits/levels;

• Each orbit/level can hold a maximum number of electrons ( 1st = 2, 2

nd = 8, 3

rd = 8 or 18, etc…)

• Move so rapidly around the nucleus that they create an electron cloud

• Mass is insignificant when compared to protons and neutrons (smallest)

• = to number of protons, in a neutral atom

• Involved in the formation of chemical bonds

Valence Electrons:

• _________________________________________________________________________________

• Electrons that can be gained, lost or shared in ____________________________________________

• How many valence electrons does this atom have?

• What element is this atom? __________________________________________________________

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Bohr Model:

• Even though this model is not correct, we use it to easily visualize what is happening with protons,

neutrons and electrons.

• How do we know that this model is Nitrogen? ___________________________________________

__________________________________________________________________________________

Lewis Dot Structure:

• Lewis Dot Structure shows the number of valence electrons for atoms.

• How many valence electrons does this atom of Nitrogen have? _____________________________

• How many total electrons does it have? ________________________________________________

Draw the Bohr Model of each Atom:

Hydrogen: Oxygen: Sodium:

Sub-Atomic Particle Weight Comparison:

Neutron=1.6749286x10-27

kg

Proton=1.6726231x10-27

kg

Electron = 9.1093897 x10-31

kg

Which particle is smallest? ________________________________________________________________

Which two particles are very similar in size (mass)? ____________________________________________

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Atomic Number:

Same as _________________________________________________________________________

What is the atomic number of this atom? _______________________________________________

Draw this an easier way:

Mass Number:

• _________________ + ______________________

• Tells us the number of protons and neutrons in an atom’s nucleus

• Expressed in Atomic Mass Units (amu)

• Each proton or neutron has a mass of 1 amu

• What is the mass number of the above atom? ____________________________________________

• Why don’t we care about the number of electrons? _______________________________________

_________________________________________________________________________________

What are the atomic and mass numbers (amu) for the following atoms?

Atoms Protons Neutrons Electrons Mass

Number

Atomic

Number Bohr Model

Carbon 6 6 6

Beryllium 4 5 4

Oxygen 8 8 8

Lithium 3 4 3

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Sodium 11 12 11

Average Atomic Mass:

• The weighted average of the masses of all the naturally occurring ____________________________

_________________________________________________________________________________

• The average considers the percent abundance of each isotope in nature

• Found on the periodic table of elements

Ion:

• _________________________________________________________________________________

_________________________________________________________________________________

• If I gain electrons, I get a negative charge _______________________________________________

• If I lose electrons I get a positive charge ________________________________________________

Build the following ions, and determine their atomic and mass numbers.

Atoms Protons Neutrons Electrons Mass

Number

Atomic

Number Bohr Model

Carbon (C3-

) 6 6 9

Hydrogen

(H1+

) 1 0 0

Oxygen (O2-

) 8 8 10

Lithium (Li3+

) 3 4 0

Sodium (Na1-

) 11 12 12

***Be aware that the atomic and mass numbers are not impacted by the loss or gain of electrons.

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Acids and Bases and the pH Scale: (Draw and label the pH Scale)

pH Scale : ______________________________________________

Acids and Bases:

Acid:

• ______________________________________________________________________________

• ______________________________________________________________________________

• ______________________________________________________________________________

• ______________________________________________________________________________

Base (alkaline):

• ______________________________________________________________________________

• ______________________________________________________________________________

• ______________________________________________________________________________

• ______________________________________________________________________________

****pH of 7 is neutral; neither an acid or a base

Section 2: Forces in the Atom:

Key Ideas:

• Understand the magnitude and range of the four fundamental forces

• Recognize the effect of each force on the structure of matter

Vocab:

• Gravitational Force - Strong Nuclear Force

• Electromagnetic Force - Weak Nuclear Force

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Forces

Gravitational Electromagnetic Strong Nuclear Weak Nuclear

• _________________

_________________

_________________

• The amount of

gravity between

objects depends on

their masses and the

distance between

them

• ________________

________________

• ________________

________________

________________

________________

• ________________

________________

• ________________

________________

________________

________________

• ________________

________________

• This force plays a key

role in the possible

change of sub-atomic

particles.

– For example, a

neutron can

change into a

proton(+) and

an electron(-)

• The force responsible

for radioactive decay.

• Radioactive decay

process in which the

nucleus of a

radioactive (unstable)

atom releases nuclear

radiation.

Section 3: The Periodic Table

Key Ideas

• Relate the properties of atoms and their position in the periodic table to the arrangement of their

electrons

Vocab

• Periodic Table - Metal

• Group - Non-Metal

• Period - Metalloid

What is the Periodic Table of the Elements?

• _________________________________________________________________________________

• Resource Information: Nova Interactive Periodic Table

First Organizers:

Dmitri Mendeleev (late 1800’s), Russian chemist

• Organizes first periodic table based on atomic mass, but some elements are out of order

Henry G.J. Moseley (1913), British chemist

• Arranged elements by atomic number, which is what we use today

• Student of Rutherford

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How is the Periodic Table Actually Organized?

Groups:

• ___________________________________________________________________________

• ___________________________________________________________________________

• ___________________________________________________________________________

• Example: Every element in group 1, has 1 electron in its outer shell, every element in group

2, has 2 electrons in its outer shell, and so on (excluding transition metals)

****Remember: Valence Electrons are electrons in the last “shell” or energy level of an atom

Important because:

• Determine an elements ability to “bond” with another element

• Chemical properties depend almost entirely on the configuration of the outer electron shell

(reactivity, flammability, etc.)

Periods:

• ___________________________________________________________________________

• ___________________________________________________________________________

• Each row in a period ends when an outer energy level is filled

• Example: Every element in the top row has 1 orbital for its electrons, 2nd

row has two orbitals

and so on

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Categories of elements in the periodic table:

Alkali Non-Metal

Alkaline Earth Halogens

Transition Metals Noble Gas

Basic metal Lanthanide (rare-earth) - radioactive

Semi metal Actinides (rare-earth) - radioactive

3 Main Categories (you have to know!!!!)

Metals:

• ________________________________________________________________________________________

• All but Mercury are solid at room temp

• ________________________________________________________________________________________

• Alkali Metals – (Group 1) are the most reactive of all metals; don’t occur in nature in their element form

• Alkaline Earth Metals – (Group 2) shiny, ductile and malleable; combine readily with other elements

• Transition Metals – (Group 3 – 12) most familiar metals because they often occur in nature uncombined

• Inner Transition Metals

• Lanthanide Series – elements with atomic # 58-71

• Actinide Series – elements with atomic # 90 - 103

Non-Metals:

Elements that are:

• _________________________________________________________________________________

• are poor conductors

• _________________________________________________________________________________

• Noble gases – (Group 18) exist as isolated atoms. They are all stable because the outer energy level

is filled.

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Metalloids:

• _________________________________________________________________________________

• Have metallic and non-metallic properties (share characteristics with metals and non-metals)

• Part of the mixed groups (groups 13, 14, 15, 16 and 17) – which contain metals, non-metals and

metalloids

How to read the periodic table: (KNOW THIS)

Practice:

Choose 3 elements and draw the box from the periodic table and the Bohr model for each.

1.

2.

3.