This document provides an overview of atomic structure and bonding. It defines key terms like elements, atoms, subatomic particles, isotopes, ions and molecules. Atoms are made up of protons, neutrons and electrons. The number of protons defines the element and isotopes can have different numbers of neutrons. Electrons determine whether an atom is neutral or an ion. Atoms combine to form compounds and the smallest units of compounds are molecules. The mole is used to quantify very large numbers of small particles like atoms and molecules, with one mole equal to Avogadro's number of 6.022x1023 particles.

1. CHAPTER 2:
ATOMIC STRUCTURE AND BONDING

2.  Matter is anything that takes up space
and has mass.
 All matter is made of atoms
 Atoms are the building blocks of matter,
sort of how bricks are the building
blocks of houses.

3. What are elements?
 Elements are the alphabet to the
language of molecules.
 To make molecules, you must have
elements.
 Elements are made of atoms. While the
atoms may have different weights and
organization, they are all built in the
same way.

4. Subatomic Particles
 Atoms composed of smaller subatomic
particles
 charged (+ or –)
 uncharged (neutral)
 electrical nature of the atom was crucial to
discovering its subatomic structure
 Law of electrostatic attraction
 like charges repel
 unlike charges attract

5. A Coulomb (C) is an amount just like “a
dozen” is an amount.
1C = 6.24x1018 the charge of electrons

6. Comparison of Subatomic Particles
Particle Location Charge(C) Mass (g) Mass
(amu)
Proton Inside
nucleus
1.602 x 10-19 1.67x10-24
1.0073=
1
Neutron Inside
nucleus
0 1.68x10-24 1.0087=
1
Electron Outside
nucleus
-1.602 x 10-19 9.11x10-28
0.0006=
0

7. Atomic structure
 Atoms are neutral
 numbers of protons and electrons must be
equal
 Atomic mass = p + n
 don’t have to worry about mass of e since
they have such a small mass (negligible)
 numbers of neutrons are determined from
atomic mass

8. Atomic Composition
• protons and neutrons are in the
nucleus.
• the number of electrons is equal to the
number of protons.
• electrons in space around the nucleus.
• Atoms are extremely small. One
teaspoon of water has 3 times as many
atoms as the Atlantic Ocean has
teaspoons of water.
The atom is mostly empty space

9. Atomic Number, Z
 All atoms of the same element have the
same number of protons in the nucleus, Z.
13
Al
26.981
Atomic number, Z
Elemental symbol
Atomic mass (u)

10.  The average mass of one atom of an element
expressed in amu.
Atomic Weight

11. Mass Number
A = mass number = number of protons + number of
neutrons
The following notation is often used
X
A
Z
Elemental Symbol
Mass number
Atomic number

12.  C-12 atom has 6 protons and 6 neutrons
 Mass Number (A) = # protons + # neutrons
 Elements with different number of neutrons
are called “Isotopes”. (Note: isotopes are
CHEMICALLY identical!)
Mass Number, A

13. Fluorine; symbol = F
 atomic number = 9
 this is the number of protons in the nucleus
 number of e = 9
 same as the number of protons for a neutral atom
 mass number = 19
 atomic weight from periodic table = 18.998
 mass number = p + n
 neutrons = 19 – 9 = 10

14. Symbolic representation
F
19
9
mass number
# protons + # neutrons
atomic number
# protons
F
19
9
has 9 protons and 10 neutrons

15. Ions (Atoms with charge)
 An atom that has either lost or gained one or more
electrons.
 Gaining electrons means more negative than positive
charges, so the ion is (-)
 Loosing electrons means more positive than negative
charges, so the ion is (+)

16. Atomic Mass Units (amu):
roughly equal to the mass of a proton or neutron.
**the mass of an atom is measured in amu’s
1 amu = 1.66x10-24g
Atomic Mass
• The mass of an atom is determined using the number
of protons and neutrons in it. (electrons are ignored)

17. How many protons and electrons does a magnesium
atom have?
What will the charge be if it loses 2 electrons?
No. of protons: 12 (+)
No. of electrons: 10 (-)
Charge of Ion 2+
Write it like this:
Mg2+

18. Isotopes
 Existence of isotopes means all atoms of an
element are not exactly the same
 all atoms of the same element have the same
number of protons in the nucleus
 atoms of the same element can have different
numbers of neutrons in the nucleus

19. Isotopes
 For a given element “X”, an isotope is written by:
 Atomic number (Z) = number of protons in the
nucleus.
 Mass number (A) = total number of protons and
neutrons in the nucleus.
X
Z
A
One proton or neutron
has a mass of 1 amu
(Atomic Mass Unit)
a.k.a “Dalton” or u
Isotopes have the
same Z but different
total number of
nucleons (A).

20. Hydrogen has 3 isotopes
1 proton and 0 neutrons, protium
1 proton and 1 neutron, deuterium
1 proton and 2 neutrons, tritium
1
1H
3
1H
2
1H
Hydrogen Isotopes

21. Periodic Properties
 Elements were first arranged by increasing
atomic number.
 Periodic table was arranged before e–
configurations of elements was known.
 Dmitri Mendeleev (Russia)
 Lothar Meyer (Germany)

22. The Periodic Table
 Dmitri Mendeleev
(1834-1907)
developed the
modern periodic
table.

23. Periodic Table Essentials
 Periods
 Metals
 Nonmetals
 Metalloids
 Halogens
 Noble Gases
 Alkali metals
 s,p,d, and f
 Lanthanide and Actinide series

24. Periodic Table Features

25. Regions in the Periodic Table

27. Compounds and Molecules
 COMPOUNDS are a combination of 2
or more elements in definite ratios by
mass.
 MOLECULES are the smallest unit of a
compound that retains the
characteristics of the compound. (non-
metal combined with a non-metal)

28. Mole
 The counting unit for atoms, molecules
ions, etc.
 1 mole of things = 6.02 x 1023 things

29. The Mole…
 The mole is the unit we use to COUNT
“things”
 It’s a really BIG number, so we use it to
count really SMALL “things”…atoms,
molecules…

30. Avogadro’s Number
602,000 million  million  million
A BIGnumber
602,000,000,000,000,000,000,000

31. The Chemist Dozen
 Socks
 Eggs
 Pencils
 Paper
 Atoms
Molecules/ions
 Pair 2
 Dozen 12
 Gross 144
 Ream 500
 Mole 6.02 x 1023

32. 6.0221415  1023
“Avogadro’s Number”
Named for Amedeo Avogadro
1776-1856
There is Avogadro’s number of particles in a
mole of any substance.
Particles and the Mole

33. Counting Atoms: The Mole
Chemistry is a quantitative
science—we need a
“counting unit” the:
1 mole is the amount of
substance that contains as
many particles (atoms,
molecules) as there are in
12.0 g of 12C.
MOLE
518 g of Pb, 2.50 mol

34. One-Mole Amounts

35. Molecular mass vs Molar mass
 Molecular mass is a number equal to
the sum of the atomic masses of the
atoms in a molecule.
 mass of 1 molecule in amu
 Molar mass
 mass of 1 mole in grams