Chapter 1: Atomic Structure

What is an atom?

the smallest particle in any substance

Why are atoms electronically neutral?

Because the positive protons are equal to the negative electrons, so they cancel each other.

Define atomic number

The number of positive protons inside the nucleus

Define mass number/nucleon number

The total number of protons and neutrons inside the nucleus.

Number of neutrons =

mass number — atomic number (kbir-small)

Explain why atomic no. and mass no. of Hydrogen are the same?

Because it has no neutrons.

What are isotopes?

Atoms of the same element that have the same atomic number but different mass number.

Isotopes have sane chemical properties?

Because they have the same electronic configuration and number of electrons in the outer shell.

Isotopes have different physical properties?

Because they have different mass & density

Across a period, …. ….. is added …..

One electron is added in the outer shell.

Down the group, …. …. is added.

One shell is added.

Group number=

Outer shell electrons.

Period number=

number of shells.

G1 in the periodic table are

Alkali Metals

G2 in the periodic table are:

Alkaline Earth metals

G7 in the periodic table are:

Halogens

G8 in the periodic table are:

Noble (inert) gases (full outer shell)