This document provides an overview of atomic structure and models of the atom. It discusses Dalton's atomic theory, subatomic particles including protons, neutrons, and electrons. Atoms are composed of a nucleus containing protons and neutrons, with electrons orbiting the nucleus. Elements differ based on their number of protons. Isotopes are versions of the same element that differ in their number of neutrons. The structure of atoms is further explained through electron configuration diagrams and quantum numbers that describe the location of electrons. Later atomic models such as the Bohr model and electron cloud model improved upon representing the structure and behavior of electrons.

1. Atomic Theory and
the Structure of
Atoms
CHAPTERS 4 & 5

2. An overview of the atom..
Atoms are extremely small
Atoms are mostly empty
space.
Reactions are the
rearrangements of atoms.

3. Law of Definite Proportions
The same compound always has the
same ratios of elements (mass)
Water – 2 hydrogen and 1oxygen
Carbon Dioxide-1 carbon and 2oxygen

4. Law of Multiple Proportions
 Atoms of the Same elements can combine in
different ratios
 Water-H2O
 Peroxide-H2O2
 Carbon Dioxide CO2
 Carbon Monoxide CO

5. Dalton’s Atomic Theory
 All matter is composed of extremely small particles called atoms.
 Atoms of a given element are identical in size, mass, and other
properties. Atoms of different elements differ in size, mass, and other
properties.
 Atoms cannot be subdivided, created, or destroyed.
 Atoms of different elements can combine in simple whole number
ratios to form chemical compounds.
 In chemical reactions, atoms are combined, separated, or
rearranged

6. Subatomic Particles
Name Location Mass Charge
Protons Nucleus 1amu +1
Neutrons Nucleus 1amu 0
Electrons Orbitals (in electron
cloud)
O amu -1

7. What is the Structure of an Atom?
Elements are different because
they have different numbers of
protons.
The Atomic Number is the number
of protons.

8. Mass
The mass of an atom is the
total number of protons and
neutrons. So the mass of an
atom is located…
These are sometimes called
nucleons

9. Charge
An atom is neutral, so the
number of electrons is the
same as the number of
protons.

10. Practice
Element Name Protons Neutrons Electrons
C
sulfur
8
35 45

11. Practice
Element Name Protons Neutrons Electrons
C carbon 6 6 6
S sulfur 16 16 16
O oxygen 8 8 8
Br bromine 35 40 35

12. Isotopes: versions of an element
with differing number of neutrons
 Because the number of neutrons is
different the mass is different and that is
how the isotopes are named.
Examples to KNOW:
Carbon-12 & carbon-14
Hydrogen, deuterium, and tritium

13. Isotope:
Name Atomic
number
Mass number protons neutrons
Carbon-12 12
Carbon-14 14
hydrogen 1
Deuterium 2
Tritium 3

14. Isotope:
Name Atomic
number
Mass number protons neutrons
Carbon-12 6 12 6 6
Carbon-14 6 14 6 8
hydrogen 1 1 1 0
Deuterium 1 2 1 1
Tritium 1 3 1 2

15. Ions: an atom with a charge
A charge is the result an in balance
of protons and electrons. This
happens when an atom gains or loses
electrons.
A negative charge means more
electrons; positive means less
electrons.

16. IONS
Element Atomic
Number
Protons Electrons
Cl-1 17 17
H+1 1 1
O-2 8 8
Ca+2 20 20

17. IONS
Element Atomic
Number
Protons Electrons
Cl-1 17 17 18
H+1 1 1 0
O-2 8 8 10
Ca+2 20 20 18

18. Mass Number
 The mass number of an atom, ion or
isotope is the total number of nucleons.
 Carbon-14; 14C; mass = 14amu
 Carbon; carbon-12; 12C; mass = 12 amu
 So how could you write
Dueterium
Tritium

19. Average Atomic Mass(atomic mass)
The weighted average of the
isotopes found in a natural sample.
 for each isotope multiple mass by
decimal form of %abundance
Find the sum.

20. Sample Problem
 Copy one of the Many examples !

21. MODELS
Models are constructs to
explain ideas and theories.
As _____ are gather the
models have been improved

22. Bohr model
Based on spectra data.
Electrons were found in
orbitals. Electrons can absorb
energy and move to higher
orbitals-___________ state.
The ________ state is the lowest
energy level.

23. Orbitals/Energy levels/shells
Energy Level # electrons
1 2
2 8
3 8
4 18
5 18

24. Skill: You should be able to draw a
Bohr diagram for elements 1-20

25. Limits of Bohr model
Only really worked for hydrogen.
Uncertainty principal- regions of
space where likely to find them-
electrons repulsion.
Spin- balances by only 2/shell

26. The Electron Cloud
LEQ: How electron arranged in the
electron cloud?

27. Quantum Numbers
Quantum Number What does it mean
Principal quantum
Number (n)
Describes the size of the energy level
Angular Quantum
number (l)
Describes the shape of the orbital (S<PD<F)
Magnetic Quantum
Number (m)
Describes the orientation of the orbital
Spin Quantum
Number (s)
Describes if the electron is spinning clockwise or counter clockwise

28. Level Orbital
s
Sub-
orbitals
Number
of
orbitals
#Electrons
1 s 1 1 2
2 S
p
1
3
4 2
6 =8
3 S
P
D
1
3
5
9 2
6
10 =18
4 S
P
1
3
16 2
6

29. SKILL: Put an example of each.
 Orbital Diagram
 Electron Configuration Notation (spdf)
 Lewis Dot Diagrams

30. Location on Periodic Table indicated
orbital being filled.