Acids and Bases - Atomic Structure

Question 1

Define element

Answer 1

A substance consisting of the atoms that are the same. They are chemically the simplest substances and therefore cannot be broken down using chemical methods.

Question 2

Atomic number

Answer 2

The number of protons/electrons an atom has.

Question 3

Mass number

Answer 3

The number of protons and neutrons.

Question 4

How are ions formed?

Answer 4

During a chemical reaction, atoms want to get a full valence shell if they do not already have one, to become stable. They do this by losing or gaining electrons, and this forms an ion.

Question 5

What is the difference between an ion and an atom

Answer 5

An ion has a positive/negative charge due to the electrons (gained/lost) being more/less than number of protons, and has a full outer shell. Whereas atoms are electrically neutral due to the SAME number of protons and electrons.

Question 6

How to name ions?

Answer 6

• positive ions (metals and H) are named after the element with “ion” at the end eg calcium ion (Ca2+)
• negative MONATOMIC ions have the suffix -ide. eg Chloride, oxide
• polyatomic ions usually have “ate” like sulphate, nitrate. Exceptions: OH- = hydroxide, NH4+ = ammonium

Question 7

What is ionic bonding?

Answer 7

Ionic bond is the FORCE OF ATTRACTION between ions that HOLDS ions together in an IONIC SUBSTANCE due to the STRONG ELECTROSTATIC ATTRACTIONS between OPPOSITELY charged ions.

Question 8

What are positive ions called?

Answer 8

Cations eg Mg2+

Attracted to the NEGATIVE cathode.

Question 9

What are negative ions called?

Answer 9

Anions eg Cl-

Attracted to the POSITIVE anode.

Question 10

What is an ionic compound?

Answer 10

When an anion bonds to a cation, the resulting compound is ionic compound because it involves IONIC BONDING

Question 11

How are ions in an ionic compound arranged?

Answer 11

In a 3D lattice. - regular grid-like pattern.

Each anion is surrounded by cations, and each cation is surrounded by anions

Held together by the strong electrostatic attraction between the oppositely charged ions. Because this bond is very strong, it takes a lot of energy to break the bonds so melting and boiling points are high.

Question 12

Rule of writing formulae?

Answer 12

Always cation (positive) ion first!

Question 13

Do chemical compounds formed during a chemical reaction have an overall charge?

Answer 13

NO

Question 14

Properties of ionic compounds? (4)

Answer 14

• Hard
• brittle
• don’t conduct electricity in solid form. If dissolved in a solution, ions are free and conduct electricity.
• High melting and boiling points - attractions of charges are very strong.

Question 15

Whats the difference between ionic bonds and covalent bonds

Answer 15

• Covalent bonds form molecules whereas ionic bonds form compounds
• Covalent bonds don’t as readily dissociated/dissolve as easy as ionic compounds.
• Low melting and boiling points because molecules are easier to separate than lattices.

So ionic compounds dissolve/dissociate easier whereas covalent bonds change states easier.

Question 16

Which elements exist as diatomic molecules in nature?

Answer 16

Halogens
Hydrogen
Oxygen
Nitrogen