Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Unit 2/B: Chemical Interactions

Chapter 5: Atomic Structure and the Periodic Table

Chapter 6: Chemical Bonds and Compounds

Chapter 7: Chemical ReactionsChapter 8: Solutions

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Chapter 5: Atomic Structure and the Periodic Table

5.1 Atoms are the smallest form of elements5.2 Elements make up the periodic table

5.3 The periodic table is a map of the elements

A substance’s atomic structure determines its physical and chemical

properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.3 The periodic table is a map of the elements

Before, you learned:•The periodic table is organized into groups of elements with similar characteristics•The periodic table organizes elements according to their properties

Now, you will learn:•How elements are classified as metals, nonmetals, and metalloids•About different groups of elements•About radioactive elements

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Warm-up questions

• Refer to the periodic table – how are each pair of elements related?

• Calcium and barium• In the same group• Lithium and carbon • In the same period• Uranium and curium • In the same period and in the actinide series

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Numbers and Mass Numbers

• All atoms are composed of the same particles…– Different numbers of protons in the nucleus

• Atomic number = # protons in the nucleus• Atomic mass number = # protons + # neutrons

– Same elements have same # protons but not always the same # neutrons, so may have different atomic masses

– Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes

– Isotopes: atoms of the same element that have a different number of neutrons• Chlorine-35, Chlorine-37

– # protons? # neutrons?

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

How to Read the Periodic Table?

1. The number at the top is the atomic number = # protons in the nucleus

2. Chemical symbol - one or two letters; temporary symbols for not-yet named elements have three-letter symbols

3. Name of element4. number at bottom is the

“average atomic mass” of all the isotopes of the elements

Color of symbol is the state of matter at room temperature

Color of background color of box indicates whether metal, nonmetal, or metalloid (5.3)

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Groups and Periods• Elements in a vertical column show similarities in their

chemical and physical properties– Known as a group– Labeled by a number at the top of the column– Sometimes a group is called a family of elements because they

seem to be related– Ex: Group 17 – “Halogen” group

• Tend to combine easily with other elements and compounds, especially elements in Gropus 1 and 2

• Different physical properties– At room temperatures: Flourine and chlorine are gases, bromine is a liquid,

iodine and astatine are solids

– Ex: Group 1 – • Some metals – lithium, sodium, potassium, for example – react

violently with water

• Horizontal row in the periodic table = period– Properties of elements change in a predictable way from one

end of a period to the other– Ex: Period 3 = elements on far left are metals, far right are

nonmetals

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The periodic table has distinct regions

• Like a map!• Different areas indicate the properties of the elements• Three main regions:

– Metals on the left (yellow)– Nonmetals on the right (except hydrogen) (green)– Metalloids in between (purple)

• Reactive – how likely an element is to undergo a chemical change – combining with other materials– Atoms in Groups 1 and 17 are the most reactive– Group 18 is the least reactive

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

To which group do most elements belong?• Most elements are metals – look! (yellow)• Metals

– elements that conduct electricity and heat well– have a shiny appearance– Can be shaped easily by pounding, bending, wire– Most are solids at room temperature (except _______)

Na - sodium

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

• Brass – zinc &copper

• Bronze - copper & tin

• Steel – mostly iron (some carbon)

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Reactive Metals (Group 1)

• Group 1 – the “alkali metals”– Sodium, potassium – often stored in oil to keep from air as

they react rapidly with oxygen and water vapor• Ions: ____ and ____ are important in living cells

(hint: which side of the periodic table loses/gains electrons)

• Group 2 – “alkaline earth metals”– Less reactive than the alkali metals, more reactive than

other metals– Calcium ions – essential to bones, teeth– Magnesium – light, inexpensive metal – combined with

other metals – airplane frames

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Transition Metals• Groups 3-12

– Copper, gold, silver, iron– Generally less reactive than most other metals

• Jewelry and coins: Gold and silver – easily shaped and not reactive – used for thousands of years

• Artifacts found in museums: unchanged -they last• Coins: Dimes and quarters made of nickel – pennies made of zinc and copper• Industry:

– Iron – main part of steel– Electric wires & Pipes – copper

• Modern Technology – tungsten – incandescent light bulbs– Alloys – two or more metals combined

• Can be stronger , less likely to corrode, or easier to shape than pure metals• Steel: iron + [nickel, chromium, manganese] (stronger than iron alone)• Brass: copper + zinc (stronger than either alone)• Jewelry: silver + copper (stronger than silver alone)

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Rare Earth Elements (metals)

• Top row of the two rows of metals shown outside the main body of the periodic table

• “Lanthanides” (they follow lanthanum on the table)

• Once believed only to be found in tiny amounts in Earth’s crust– Not as rare as originally thought – just hard to

isolate in pure form

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Nonmetals and metalloids

• Have a wide range of properties• Nonmetals: – Many are gases at room temperature– One is a liquid (Bromine)– Solids often have a dull surface and cannot be shaped by

hammering or wires– Poor conductors of heat and electric current– Ex: air – nitrogen and oxygen – both gases, different

properties• Nitrogen is fairly unreactive• Oxygen readily reacts – rusting, burning

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Halogens (nonmetals)

• Group 17– Halogens means “forming salts”– Very reactive• Often used to kill harmful microorganisms

– Ex: chlorine, iodine

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Noble Gases (nonmetals)• Group 18– Noble = inert gases – almost never

react with other elements– Ex: colorful lights – pass an electric

current through tubes of neon, krypton, xenon, argon gases glow

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Metalloids

• Properties of both metals and nonmetals• Most common is silicon (Si)– The second most common atoms in Earth’s crust

• Uses:– Semiconductors found in electronic devices• Conduct electricity under some conditions and not

under others• Used in computer chips (silicon, gallium, germanium)

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Some atoms can change their identity

• How is identity determined?• # protons in _________• The nucleus• Chemical changes do not affect the nucleus, so

chemical changes don’t change one type of atom into another

• BUT…conditions may cause the number of protons to change…does this change the type of atom?

• Yes!

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Some atoms can change their identity• Stability of a nucleus depends on the right balance of

protons and neutrons– Too few or too many neutrons, the nucleus may become

unstable– Particles are then produced from the nucleus of the atom to

restore balance• Results in a release of energy• May change the number of protons different element!

– Radioactivity – the process by which atoms produce energy and particles• Isotope is radioactive if the nucleus has too many or too few neutrons

– Radioactive isotopes are more rare for lighter elements more common for heavier

• Measured using a Geiger counter – detects particles from the break up of the atomic nucleus - clicks

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Radioactivity and Medicine

• Used to diagnose and treat patients– Destroy harmful tumors– Monitor activity of certain organs in body – inject

a radioactive isotope and determine where and how the body is using a substance

• Large does are harmful– Damage or kill cells– Energy from its particles can burn the skin– Prolonged exposure linked to cancer

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Radioactive Decay

• Energy and particles are produced from the nucleus of radioactive atoms• Radioactive decay – when the number of protons, and the identity of the

atom, changes• Occurs at a steady rate characteristic of the particular isotope• Half-life – the amount of time it takes for one-half of the atoms in a particular

sample to decay– Ex: 1000 atoms of radioactive isotope with half-life of 1 year…how many atoms

would have changed one year later? After another year?– Not affected by temperature or pressure– Can range from fractions of a second to billions of years

• Simulation: http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html• Animation: http://holbert.faculty.asu.edu/eee460/eee460.html