chapter 2 - atomic structure

ATOM

Atom is the smallest particles which is indivisible.

Historical development of atom JOHN DALTON

atom cannot be created or destroy

J.J THOMPSON atoms have electron scattered inside it.

ERNEST RUTHERFORD nucleus has positive charge

NIEL BOHR his proposed, atom model based on the solar system.

JAMES CHADWICK in nucleus, have neutron that has no charges.

Structure of atom

SUBATOMIC PARTICLES

Proton Neutron

Electron

SIMILARITIES:

1)They are subatomic particles.

2)Proton and neutron have the same mass.

3)Proton and neutron are located in the nucleus

Differences:Particles/ properties

Proton Electron Neutron

Charge Positive Negative Neutral (no

charge)

Location In nucleus Around nucleus

In nucleus

Relative mass

1 1/1840 1

Motion Stationary Move around

nucleus in a fixed orbit

Stationary

Symbol p e n

Proton number

Proton number is the number of protons in an atom of an element.

Elements can be differentiated by referring to their proton number.

Nucleon number

Nucleon number is a total number of protons and neutrons in an atom of an elements.

Nucleon number = number of protons + number of neutron

In a neutral atom, the proton number also refers to the number of electrons in that atom.

In neutral atom, Proton number = number of

protons

= number of electrons in a

neutral atom.

CALCULATION OF NUCLEON NUMBER Example 1:

The following information is regarding the subatomic particles of atom P:

proton number = 13neutron number = 14

What is the nucleon number of atom P?

Example 2

Oxygen atom has 8 number of protons and 8 number of neutron. The nucleon number of oxygen atom is _______.

Exercise 1

In the sodium atom nucleus has 11 number of protons and 12 number of neutron. So, the nucleon number is _____.

Exercise 2

The nucleon number of calcium atom is 40. The proton number of calcium atom is 20. How many the neutrons number in the atom calcium?

Exercise

Atom

Number of

proton

Number of neutron

Nucleon

number

Number of

electron

P 8 8Q 24 12R 19 39S 20 20

Question To Try

1)What is the name of the positive particles of an atom?

2)Where are electrons located in an atom?

3) If an element X has 9 protons and 10 neutrons, what is its nucleon number? How many electrons are there in X?

PROTON Symbol: pCharge: +1Relative mass: 1Location: in the nucleus

NEUTRON

Symbol: nCharge: 0Relative mass: 1Location: in the nucleus

ELECTRON Symbol: e Charge: -1 Relative mass: 1 (negligible)

1840 Location: surrounding the

nucleus in a certain orbit