Explaining the Periodic Table (6.7)• If elements are the building blocks of all other matter, what

are they made of?

• There are three particles that make up an atom or element: • protons• electrons• neutrons

•These are called subatomic particles because they are smaller or below an atom.

PROTONS are located in the nucleus and have a positive charge. NEUTRONS are also located in the nucleus and have no charge. ELECTRONS are located in orbits around the nucleus. They have a

negative charge.

Explaining the Periodic Table (6.7)How many ELECTRONS, PROTONS and NEUTRONS are in an atom?

Ccarbon

6

12.01

element symbol

element name

atomic number

atomic mass

(mass number)

Atomic Number Ccarbon

6

12.01

atomic number

• atomic number = # of protons

• each element has a unique atomic number • each element is identified by its atomic number and

number of protons • (ex. the element carbon, and only carbon, has the atomic

number of 6)

• In a neutral atom, the number of positives must equal the number of negatives.

• This means the # of electrons = # of protons

Atomic mass(mass number)

• atoms of an element may have different masses because they have different numbers of neutrons – these are called isotopes

• round mass to a whole number

Ccarbon

6

12.01

atomic mass

(mass number)

mass number = sum of protons + neutrons

From the atomic number and mass number of an atom, we can determine the number of protons, electrons, and neutrons in an atom.

# protons = atomic number# electrons = # protons (for neutral atoms only)# neutrons = mass number – atomic number

Ex) Determine the number of protons, electrons and neutrons in the following atoms:

a) Fluorine b) Bromine c) Sodium

____ protons ____ protons ____ protons

____ electrons ____ electrons ____ electrons

____ neutrons ____ neutrons ____ neutrons

99

10

3535

45

1111

12

Bohr-Rutherford Models of the

Elements

Bohr-Rutherford diagrams are drawings of atoms that show the number of protons and electrons in the nucleus and the number of electrons in each energy level (orbit).

Ex) 1st orbit can hold 2 electrons

The 2nd and 3rd orbits can hold 8 electrons

Let’s try drawing Bohr-Rutherford Models:

1 HHydrogen

10

1

5 BBoron

56

2-3

10 NeNeon

1010

2-8

13 AlAluminum

1413

2-8-3

16 SSulphur

1616

2-8-6

19 KPotassium

2019

2-8-8-1