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Chapter 3: Atomic Structure

y102023001 — 2024-04-23 03:47:45 UTC

ATOMIC STRUCTURE :-)

y102023012 — 2024-04-23 03:48:00 UTC

3.3 Arrangement of Electrons in Atoms

y102023001 — 2024-04-23 03:53:56 UTC

The electrons in an atom move around the nucleus in regions known as electron shells.

3.1 What are inside atoms?

y102023012 — 2024-04-23 03:57:09 UTC

WHAT IS AN ATOMIC STRUCTURE?

All substances are made of tiny particles of matter called atoms which are the building blocks of all matter
Each atom is made of subatomic particles called protons, neutrons, and electrons
The mass of the electron is negligible, hence the mass of an atom is contained within the nucleus where the protons and neutrons are located

Electronic configuration

y102023001 — 2024-04-23 04:01:49 UTC

The arrangement of electrons in an atom can be represented using electronic configuration.

Example:

A magnesium atom has 12 proton. --> Its electronic configuration can be written as 2,8,2

charges , mass , symbol

y102023012 — 2024-04-23 04:10:00 UTC

🎀 The size of atoms is so tiny that we can't really compare their masses in conventional units such as kilograms or grams, so a unit called the relative atomic mass is used

🎀One relative atomic mass unit is equal to 1/12^ththe mass of a carbon-12 atom.

PROTON SYMBOL = p

NEUTRON SYMBOL= n

ELECTRON SYMBOL = N

3.2 Proton Number and Nucleon number

y102023012 — 2024-04-24 01:07:35 UTC

The Proton Number (Atomic Number) is the number of protons in the nucleus of an atom.
It is unique to each element. It is denoted by the letter “Z”. For a neutral atom, the number of protons and electrons are equal; therefore, the proton number (Z) also corresponds to the number of electrons.
The Nucleon Number (Mass Number) is the total number of protons and neutrons in the nucleus of an atom.
Mass number = number of protons + number of neutrons
Number of protons = mass number – number of neutrons
Number of neutrons = mass number – number of protons

3.4 ISOTOPES

y102023012 — 2024-04-24 01:12:56 UTC

--> different atoms of the same element with the same number of protons but different numbers of neutrons.

The isotopes of an element have the same chemical properties because they contain the same number of outer shell electrons and, therefore, have the same electronic configuration.
The difference in mass affects the physical properties, such as density, boiling point and melting point

Relative Atomic Masses

y102023012 — 2024-04-24 01:23:01 UTC

Most elements exist naturally as a mixture of their isotopes. Using the data on the abundance of these naturally occurring isotopes, we can calculate the mass relative atomic mass of the element.

EXAMPLES :

1) A naturally occurring sample of neon gas has two isotopes 20Ne and 22Ne . 90% of the sample is 20Ne . What is the RAM of naturally occurring neon?

100%-90%= 10% (for Ne22)

(90 x 20 + 10x22 )/ 100 = 20.0