Name:
Introduction to Atomic Structure
Year 11 Science
Ruawai College 2014
Atoms
Atoms are identified by the numbers of protons, neutrons and electrons that
they contain. Before you can understand the properties of atoms, how atoms
combine to form ionic compounds and molecules, you must be familiar with
the number of protons, neutrons and electrons associated with atoms.
Success Criteria:
 Identify the composition of atoms in terms of numbers of protons,
neutrons and electrons.
 Use atomic symbols to represent different atoms.
 Efficient use of the Periodic Table as a source of data.
Information:
The entire world is composed of atoms, and atoms are composed of protons,
neutrons and electrons. Protons and neutrons are about 2000 times heavier
than an electron. A proton has a charge of +1, a neutron has no charge and an
electron has a charge of -1. The nucleus is very dense and very small
compared to the entire atom.
Particle
electron
proton
neutron
Sub-atomic Particles
Symbol
Relative charge
e
-1
+
p
+1
o
n
0
Key Questions:
1.
What is the charge on a proton?
2.
What is the charge on an electron?
3.
What is the sub-atomic particle that has no charge?
Exercise:
4.
If an atom has 2 protons and 2 electrons, what is the overall charge of
that atom?
5.
If an atom has 6 protons and 6 electrons, what is the overall charge of
that atom?
Information:
This model shows a sodium atom.
It has protons (P) in its nucleus.
It has neutrons (N) in its nucleus.
It has electrons (-) in the electron
shells around the nucleus.
Key Questions:
6.
How many protons are in the nucleus of the sodium atom?
7.
How many neutrons are in the nucleus of the sodium atom?
8.
How many electrons are surrounding the nucleus of the sodium atom?
Exercises:
9.
What is the overall charge of the sodium atom?
10.
How did you work out the answer to question #9?
11. Does the number of neutrons make a difference to the overall charge of
the sodium atom?
12.
Explain your answer to question # 11.
Information:
A
Mass number
Atomic symbol
Atomic number
X
Z
- the element’s atomic number (Z) which indicates the number of protons
in the nucleus
- the mass number (A) which indicates the number of protons and
neutrons in the nucleus
7
Li
3
The atomic symbol for Lithium is Li
Key Questions:
13. What does Z refer to?
14.
What does A refer to?
15.
What is the atomic number of Lithium?
16.
What is the mass number of Lithium?
Exercises:
17. How many protons does a Lithium atom have in its nucleus?
18.
How many neutrons does a Lithium atom have in its nucleus?
19.
How do you calculate the mass number of a Lithium atom?
20.
How do you calculate the mass number of any atom?
Information:
The Periodic Table of Elements of the First 20 elements
Mass number
Symbol
Atomic number
1
4
1H
7
9
11
3Li
4Be
5B
23 Na 24 Mg 27 Al
11
12
13
39 K
40 Ca
19
20
12
6C
14
7N
16
8O
19
9F
28
14Si
31
15P
32
16S
35
17Cl
Key Questions:
21. What is the atomic number of H, hydrogen?
22.
What is the mass number of H, hydrogen?
23.
What is the atomic number of N, nitrogen?
24.
What is the mass number of N, nitrogen?
25.
What is the mass number of Ar, argon?
26.
What is the mass number of Ca, calcium?
Exercises:
27. How many neutrons does a hydrogen atom have in its nucleus?
28.
How many neutrons does a nitrogen atom have in its nucleus?
29.
How many protons does argon have in its nucleus?
30.
How many neutrons does argon have in its nucleus?
31.
How many protons does calcium have in its nucleus?
32.
How many neutrons does calcium have in its nucleus?
2He
20
10Ne
40 Ar
18
33. Use a periodic table to fill in the missing information in the following
table. Remember the number of protons always equals the number of
electrons in an atom.
Name
Symbol
16
8O
Atomic
Mass Number Number Number
Number Number
of
of
of
Z
A
Protons Neutrons Electrons
8
16
8
8
8
a
Oxygen
b
Nitrogen
c
Sulfur
d
Hydrogen
e
Lithium
f
Magnesium
12
g
Carbon
6
7
34
7
16S
18
1
24
h Phosphorus
i
34.
Calcium
31
40
20Ca
40
20
How do you work out the number of protons from the atomic number?
35. How do you work out the number of electrons from the number of
protons?
36.
15
How do you work out the number of neutrons?
Information:
K: 2,8,8,1
Atoms have the same number of electrons as protons. Electrons are arranged
in energy levels or shells around the nucleus. Each shell can only hold a
maximum number of electrons (2, 8, 8, 8). Shells closest to the nucleus as
filled first and the number of electrons in each shell can be written after the
element symbol.
Key Questions:
37. How many electrons are in the inner most shell of the potassium atom?
38.
How many electrons are in the second energy level of potassium?
39.
How many electrons are in the third energy level of potassium?
40.
How many electrons are in the fourth energy level of potassium?
41.
How many electrons does a potassium atom have in total?
Exercises:
42. Draw a model of an oxygen atom, showing O for the nucleus and the
electrons arranged around the nucleus in two shells. O: 2,6
43.
Fill in the missing information in the periodic table below.
Key
Atomic Number
Symbol
Name
Electron arrangement
1
1
H
Hydrogen
1
3
Li
Lithium
2,1
11
Na
Sodium
2,8,1
19
K
Potassium
2,8,8,1
2
13
4
5
12
13
14
6
C
Carbon
2,4
14
15
16
17
7
8
9
15
16
17
Cl
Chlorine
2,8,7
18
2
He
Helium
2
10
Ne
Neon
2,8
18
20
The numbers above the columns in the periodic table are Groups.
The rows of the periodic table are called Periods.
44.
Name the elements in Group 1.
45. What is similar about the electron arrangements of the elements of
Group 1?
46.
Name the elements in Group 17.
47. What is similar about the electron arrangements of the elements of
Group 17?
48. What is similar about the electron arrangements of the elements of
Group 18?