atoms & elements. what is an atom? an atom is the smallest particle of an element that retains...
TRANSCRIPT
Atoms & Elements
•What is an atom?
An atom is the smallest particle of an element that retains its identity in a chemical reaction.
Word origin: atom comes from the Greek word atomos meaning “ indivisible”
•Elements & Compounds
• What would atoms of an element, mixture and compound look like at a microscopic level?
• The parts that make up an atom!• protons • neutrons• electrons
•Subatomic Particles
nucleus
proton
neutron
electron
• Found in the nucleus
• Identifies the element
• #of protons = specific element
• Responsible for chemical and physical properties
• Found in the nucleus
• Plays no role in chemical behavior
• Purpose: to put space between protons
• Spin around in set regions outside of nucleus
• Most important in chemical reactions
• Farthest electron away from nucleus determines how atoms chemical to combine to one another.
•Subatomic ParticlesElectronsNeutronsProtons
Name Symbol Charge Relative Mass
Proton p+ +1 1
Neutron no 0 1
Electron e- -1 0 (1/1840)
•Subatomic Particles
How big is an atom?
Imagine the nucleus is the size of a marble located in the middle of the football field,
the electron would be in the classroom the size of a period!
•Periodic TableGreatest Cheat Sheet Ever!
• Rows: periods• 7 periods
• Columns: groups or families• 18 Groups
• 1A: Alkali Metals
• 2A: Alkaline Earth Metals
• 7A: Halogens
• 8A: Noble gases
• B Groups: Transition and Inner Transition Metals
•Periodic Table Categories:Metals
Nonmetals
Metalloids
(B, Si, Ge, As, Sb, Te, At)
•Periodic Table
14
SiSilicon28.086
Atomic Number
Symbol
Element name
Atomic Mass
• Counts the number of protons in an atom within the nucleus
•Atomic Number
• Important Numbers
14
SiAtomic Number = # of protons
Silicon has 14 protons
•A. Nitrogen
•B. Potassium
•C. Neon
• State the number of protons for atoms of each of the following:
•Atomic Number
•A. Nitrogen• 7 protons
•B. Potassium• 19 protons
•C. Neon• 10 protons
• State the number of protons for atoms of each of the following:
•Atomic Number
•An atom is neutral
•The net charge is zero
•Number of protons = Number of electrons
•Atomic number = Number of electrons
•Remember: proton = +1 electron = -1
•Number of Electrons
•Number of Electrons
14
Si14 protons14 electrons
-14 +14
= 0 neutral
• Counts the number of protons and neutrons in an atom
OR• Determined by: the whole number closest to the Atomic Mass
• Mass Number
• Important Numbers
14
SiSilicon28.086 Atomic Mass
• Show the mass number and atomic number• Give the symbol of the element
• Atomic Symbols
•Mass Number
2814Si
Mass Number
Atomic Number
silicon-28
•Determine the Mass Numbers
4
Be9.0122
27
Co58.933
10
Ne20.179
9 59 20
•Write the Symbol and Name for each
4
Be9.0122
27
Co58.933
10
Ne20.179
Be94
beryllium-9
5927Co
cobalt-59
2010Ne
neon-20
• The total number of particles in the nucleus• # of protons + # of neutrons
• To determine the number of neutrons• Mass number – Atomic number = # of neutrons
•Mass Number
168
3115
6530
#p
#n
#e
O P Zn
8p+
8no
8e-
15p+
16no
15e-
30p+
35no
30e-
• The atomic number identifies the element, but an element may have atoms with several different mass numbers.
• Most elements consist of several different isotopes• Same number of protons , Different number
of neutrons
• Isotopes
3517Cl 37
17 Cl
chlorine-35chlorine-37
• Naturally occurring hydrogen consists of 3 isotopes, protium (H-1), deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons.
• Isotopes of Hydrogen
11
21
31
#p
#n
#e
H H H
1
0
1
1
1
1
1
2
1
• A. Number of protons
• B. number of neutrons
• C. What is the mass number of a calcium isotope with 19 neutrons?
•An atom of Calcium (Ca-40)
• This is NOT a whole number
• A given element can have atoms with several different mass numbers.
• Average mass of the atoms with all possible mass numbers• We will calculate later
•Atomic Mass
•A. 11p+, 12no, 11e-
•B. 17p+, 20no, 17e-
•C. 47p+, 60no, 47e-
•Write the atomic symbol
•A. 11p+, 12no, 11e-
•B. 17p+, 20no, 17e-
•C. 47p+, 60no, 47e-
•Write the atomic symbol2311 Na
3717
Cl
10747
Ag
• Remember atoms are neutral, therefore if an atom has a charge we call it an ion.
• Ions- Atoms which gain or lose an electron
• Atoms with a charge (positive or negative)• Ions
atom ion#p 11 11#e 11 10
atom ion#p 17 17#e 17 18
Na1+
Cl1-
Why do the electrons change?
• If protons change…new______?________
• If neutrons change…new______?______
• If electrons change….new _____?______
•Why?
• If protons change…new element
• If neutrons change…new isotope
• If electrons change….new ion
•Why?
atomion
#p 12 12
#e 12 10
atom ion#p 8 8
#e 8 10
• Ions
Mg 2+
O 2-
• What does each represent? • How many of what subatomic particles does each represent?
•Complete Atomic Symbolcombines isotopes and ions
27
13
Al 3+
•Complete Atomic Symbolcombines isotopes and ions
27
13
Al 3+
13p+ 10e- 14no
Ionic chargeMass number
Atomic number
7p+7no10e-
15p+17no18e-
30p+35no28e-
N3- P3- Zn2+
•How many protons, neutrons, & electrons?
147
3215
6530
Coming back to this…Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.
So we involved all the different forms of ATOMS of an element (ions not an issue here) and how frequent they are
•Atomic Mass
• To find the Average Atomic Mass (generally referred to as the atomic mass of an element) we need to use two things
• The mass of the isotope• Multiplied by its frequency• Then we add all the forms up.
•Average Atomic Mass cont.
Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = 26.4 100
35.5 37 x 24.5 = 9.07
100
•Example of Average Atomic Mass
ADD US UP
•Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass or rubidium?