Atoms, Elements & Compounds 🧪

Question 1

Elements

Answer 1

A substance made of atoms that all contain the same number of protons and cannot be split into anything simpler

Question 2

Compounds

Answer 2

A pure substance made up of 2 or more elements chemically combined. Compounds cannot be separated into their elements by physical means

Question 3

Mixture

Answer 3

A combination of 2 or more substances (elements or compounds) that are not chemically combined. Mixtures can be separated by physical methods

Question 4

Atoms

Answer 4

The building blocks of all matter

Question 5

Atoms are made of subatomic particles

Answer 5

Protons
Neutrons
Electrons

Question 6

One relative atomic mass unit is equal to

Answer 6

1/12th mass of a carbon-12 atom

Question 7

Relative mass of subatomic particles

Answer 7

Proton= 1
Neutron= 1
Electron= 1/1840

Question 8

The first shell can hold

Answer 8

2 electrons

Question 9

The second shell can hold

Answer 9

8 shells

Question 10

The third shell can hold

Answer 10

8-18 electrons

Question 11

Isotopes

Answer 11

Isotopes are atoms of the same element that contain the same number of protons but a different number of neutrons

Question 12

Isotopes display the same chemical properties because

Answer 12

They have the same number of electrons in their outer shells therefore the same electronic configuration and this is what determines an atoms chemistry

Question 13

Isotopes have different physical properties because

Answer 13

The difference in mass affects physical properties such as density, boiling point and melting point

Question 14

Heavy water refers to water made from

Answer 14

Deuterium oxide. It is 20% heavier and has a relative formula of 20. Not ideal to drink because it interferes with biochemical reactions in your cells

Question 15

Relative Atomic Mass (RAM)

Answer 15

The average mass of isotopes of an element compared to 1/12th of the mass of the atom of C-12
(% of isotope * mass)+ (% of isotope * mass)/ 100

Question 16

Ions

Answer 16

An electrically charged group of atoms formed by the loss or gain of electrons (this occurs to make the atom more stable)

Question 17

Ionisation of metals

Answer 17

All metals can lose electrons to other atoms and become positively charged atoms called cations

Question 18

Ionisation of non-metals

Answer 18

All non-metals can gain electrons from other atoms to become negatively charged ions called anions

Question 19

Lattice structures

Answer 19

Formed by ionic compounds, consist of a regular arrangement of alternating positive and negative ions

Question 20

Ionic compounds

Answer 20

Formed when metal atoms and non-metal ion react. The compound has no overall charge

Question 21

Properties of ionic compounds

Answer 21

Usually solid at room temperature
High MP and BP
Good conductors of electricity in the molten state or in solution
Poor conductors in solid state

Question 22

Ionic substances have high MP and BP because

Answer 22

of the presence of strong electrostatic forces acting on oppositely charged ions. These forces act ion all directions and a lot of energy is required to overcome them. The greater the charge on the ions, the stronger the electrostatic forces and the height the MP and BP will be.

Question 23

Electrical current

Answer 23

For electrical current to flow there must be freely moving charged particles such as electrons or ions present so ionic compounds in molten form are good conductors of electricity in molten state or in solution as they have ions that can move and carry a charge. But solids have ions in a fixed position within the lattice and are unable to move

Question 24

Covalent bonds

Answer 24

Formed when pairs of electrons are shared between non-metal atoms to gain a full outer shell giving them a noble gas configuration. These atoms are now called molecules

Question 25

Properties of simple molecular compounds

Answer 25

Covalently bonded together (only a few atoms) They have low MP and BP so they are usually liquids or gases at room temp Poor electrical conductors As the size of the molecules increases their MP and BP increases

Question 26

Simple molecular compounds have low MP and BP because

Answer 26

There are only weak intermolecular forces acting between the molecules

Question 27

Electrical conductivity of small molecular compounds (explanation)

Answer 27

There are no free ions or electrons to carry the charge so they are good insulators

Question 28

Allotropes of Carbon

Answer 28

Diamond Graphite

Question 29

Diamond structure

Answer 29

Each carbon atom bonds with 4 other carbon atoms forming a tetrahedron. No intermolecular forces, very strong bonds and the substance is hard

Question 30

Properties of diamond

Answer 30

It doesn’t conduct electricity It has a very high MP It is extremely hard and dense Shiny

Question 31

Uses

Answer 31

Jewelry Cutting glass The tips of drills

Question 32

Structure of Graphite

Answer 32

Each carbon atom is bonded to 3 others forming layers of a hexagonal-shape leaving one free electron per carbon atom which exist in between layers. The layers are connected by weak vander waal’s force.

Question 33

Properties of Graphite

Answer 33

Conducts electricity Has a very high melting point It is soft and slippery, less dense than diamond

Question 34

Uses

Answer 34

Pencil lead Lubricants To make non-reactive electrodes for electrolysis

Question 35

Structure of Silicon (IV) Oxide

Answer 35

Each oxygen atom is covalently bonded with 2 silicon atoms and each silicon atom is covalently bonded to 4 oxygen molecules. A tetrahedron is formed

Question 36

Comparing diamond and SiO2

Answer 36

SiO2 has lots of very strong covalent bonds and no intermolecular forces so it has similar properties to diamond They are both very hard and have high boiling points and are insoluble in water and don’t conduct electricity SiO2 is cheap since it is available naturally

Question 37

Uses

Answer 37

To make sandpaper To line the inside of furnaces

Question 38

SiO2 is found in

Answer 38

Sand

Question 39

Metallic bonding

Answer 39

Metal atoms are held together strongly by metallic bonding in a giant metallic lattice. The atoms lose electrons from their outer shells and become positively charged ions. They move freely between the positive ions like a sea of electrons. Metallic bonds are strong and are a result of the attraction between the positive metal ions and the negatively charged delocalised electrons

Question 40

Metals have high melting and boiling points

Answer 40

There are many strong metallic bonds in giant metallic structures between positive metal ions and delocalised electrons. A lot of heat energy is required to break those bonds

Question 41

Metals conduct electricity because

Answer 41

There are free electrons available to move through the structure and carry charge. Electrons entering one end of the metal cause a delocalised electron to displace itself from the other end hence electrons can flow so electricity is conducted

Question 42

Metals are malleable and ductile

Answer 42

Layers of positive ions can slide over one another and take up different positions. Metallic bonding is not distrusted as the outer electrons do not belong to any particular metal atom so the delocalised electrons will move with them. Metallic bonds are thus not broken and as a result metals are strong but flexible. They can be hammered and bent into different shapes or drawn into wires without breaking