Atomic Structure

and BondingThe Structure of Atoms

Specific Learning Outcomes Describe or label a diagram of a model of an atom using

the terms protons, neutrons, electrons and nucleus.

Define atomic number (Z)

Define mass number (A)

Define and give examples of isotopes.

Calculate the number of electrons, protons and neutrons

in any named atom.

Write electron configurations of the first 20 elements

using 2,8,8 notation.

A little Atomic HistoryIn 1806 John Dalton reintroduced the idea of an atom. His theory suggested that all elements were made up of atoms. These atoms were unique to the element and could not be created or destroyed. When atoms from different elements joint together they would form compounds.

Amedeo Avogrado1811

Discovered that some elements

existed in combinations atoms

like Cl2 or O2

Jons Berzelius1813

Devised the “Chemical Symbol”

First letter uppercase, second letter lower case.

J J Thomson1897

Discovered electrons.

Ernest Rutherford1911

Discovered a lot more about atomic

structure – like polarity and density.

Henry Moseley1914

Learnt how to count the positive charges in an atom and how

electrons were arranged.

The Structure of AtomsElectron

(Negative Charge)

Neutron(No Charge)

Proton(Positive Charge) Nucleus

There are three pieces to an atom. There are electrons, protons, and neutrons.

As you know, there are over 100 elements in the periodic table. The thing that makes each of those elements different is the number of electrons, protons, and neutrons.

The protons and neutrons are always in the centre of the atom. Scientists call the centre of the atom the nucleus.

The electrons are always found whizzing around the centre in areas called orbitals.

Energy Level

Atomic Number and Mass NumberChemists have a symbolic way of representing atoms which enables them to quickly see how many protons, neutrons and electrons an atom has…

Mass Number

Element SymbolAtomic

NumberAtomic Number =

Number of protons in the

nucleus orNumber of

electrons outside of the nucleus

Mass Number = Number of

protons plus neutrons in the

nucleus

IsotopesAtoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes.

For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons.

Hydrogen Deuterium Tritium

Atomic Number and Mass NumberActivities

• The Structure of Atoms (page 44)• Complete Table

Level 2 Chemistry Practical Workbook

What's the most important thing to learn in chemistry?

Never lick the spoon.

Electron ConfigurationAn electron configuration of an atom is a description of the

number of electrons in each energy level.

Nucleus

1st Level

2nd Level

3rd Level

2 8 84th

Level

?

For example for the element calcium where Z = 20, the electron configuration would be as 2,8,8,2.

To complete an electron configuration take the atomic number (Z) and spread it out through the levels – each level

has a maximum number of electrons that it will hold as demonstrated above.

Whatever is left over

Electron Configuration Activities

• Electron Configurations of the First 20 Elements (page 10)• Complete Question 1 (a, c, e, g & i)• Complete Question 2 (b, d, f, h, & j)• Complete Question 3• Complete Question 4 (a & b)

Level 2 Chemistry Theory Workbook