Study Guide: Periodic Table, Atoms, & Ionic Compounds [Chemistry]

In this post we will look at the basics surrounding atoms, how to use the periodic table, ions and predicting charges, and the solubility rules. We will include some practice problems as well as solutions (Feel free to DM us on instagram for both worked solutions and further explanations).

The new syllabus is all about applying your knowledge to knew situation and chemicals that you haven't dealt with in class; and to do this, you need to know how to use these basic things to predict and work out more complex ideas.

The Atom

All matter is made up of very small particles called atoms. Inside an atom we have three subatomic particles: protons, neutrons, and electrons. The protons and neutrons can be found inside the nucleus of the atom, while the electrons are found orbiting the atom in orbital shells.

It is important for us to know the relative charge and weight of each subatomic particle, as we use these in various calculations later on. The table below summarises this information:

* Charge is measured in Coulombs (C)

** Mass is measured in grams (g)

The periodic table

The periodic table, developed by Russian chemist Dmitri Mendeleev in 1869, follows various trends that make predicting characteristics of elements very easy. The columns are called group, and the rows are called periods.

Here are the main trends found in the periodic table:

As we ready from left to write, each element increases in atomic number
Genereal the left side of the table are metals, the right side are non metals, and the elements on the dividing line are metalloids (interactive periodic table here)
Elements in the same group have the same valency
The position of an element can give us an insight into the boiling and melting point of the element

From the periodic table, we can also find out the amounts of subatomic particle each element has by looking at the mass and atomic number.

The mass number of a symbol tells us the amount of protons and neutrons an atom has, while the atomic number tells us the number of protons only (the proton number doesn't change, and is what determines what element we are looking at)

All elements have the same number of protons and electrons (in order to stay neutral)

Looking at helium we can work out the number or each subatomic particle:

Protons: 2 (from the atomic number)

Electrons: 2 (elements have the same number of protons as electrons)

Neutrons: 2 (mass number - atomic number)

Atoms, Molecules, compounds, & mixtures

For this section I just want to supply you guys with definitions and examples for atoms, molecules, compounds, and mixtures. (these are the definitions I got from my lecturer, Dr Philp)

Atoms are particles that make up all substances

e.g. hydrogen

Molecules are atoms that have bonded.

e.g H2O (water)

Compounds are pure substances consisting of atoms of more than one element. They have FIXED composition.

e.g

Mixtures are not pure substances and contain a combination of atoms, molecules and compounds.

e.g water and nitrogen gas

* Here is a helpful website to understand these visually

Ions and ionic comounds

The first thing we are going to talk about it valencies. The valency of an element tells us how many electrons an ion has either gained or lost. As electrons are negatively charged (refer to the table at the beginning) an ion that has LOST an electron will have a POSITIVE charge and an ion that has GAINED an electro will have a NEGATIVE charge. Positively charged ions are called Cations, while negatively charged ions are called anions.

Below are a list of common anions and cations that you need to learn (as they pop up often), however you can work out the valency of most elements based on its position on the periodic table!

Formulae of common cations

Formulae of common anions

To work them out, we look at the period in which the element is found. Elements in the first period will have a valency of 1+, elements in the second period will have a valency of 2+ ect (this pattern doesn't work for the transition metals).

In terms of naming ionic compounds, we write the cation first, followed by the anion.

e.g, CaCO3 will be Calcium Carbonate

If the element of a cation ends in -ine, we change it to -ide.

e.g chlorine becomes a chloride ion, and iodine becomes an iodide ion.

Practice questions:

Write the valencies of the following elements: Mercury(I), Nitrate, Zinc and sulphide
What is the atomic number of Nickel?
Is boron a metal, non-metal, or a metalloid (periodic table here)
Write an Ionic formula for Sodium Chloride (hint: Cation + anion --> Compound)
Write an ionic formula for amonium sulphate
What is the name of the compound PbCl2 ?

Answers to practice questions:

Hg(+), NO2(-), Zn(2+), and S(2-)
28
metalloid
Na(+) + Cl(-) --> NaCl
NH4(+) + SO4(2-) --> [NH4]2SO4
Lead Chloride

So we hope this was helpful to you guys!

Remember to check out our study printable here, and feel free to DM us on instagram ( @nesa.meemees ) if you have any questions!!