Chapter 3 - Atoms, Elements and Compounds

Question 1

What are elements

Answer 1

Elements are made of tiny particles of matter called atoms

Question 2

What do atoms consist of

Answer 2

Each atom is made of subatomic particles called protons, neutrons and electrons
Their size 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

Question 3

What is relative atomic mass

Answer 3

One relative atomic mass unit is equal to the mass of a carbon-12 atom.
All other elements are measured relative to the mass of a carbon-12 atom and since these are ratios, the relative atomic mass has no units

Question 4

What is hydrogens relative atomic mass

Answer 4

Hydrogen for example has a relative atomic mass of 1, meaning that 12 atoms of hydrogen would have exactly the same mass as 1 atom of carbon

Question 5

What is the atomic number/ proton number

Answer 5

The atomic number (or proton number) is the number of protons in the nucleus of an atom. The symbol for this number is Z
It is also the number of electrons present in an atom and determines the position of the element on the Periodic Table

Question 6

What is the nucleon number

Answer 6

Total number of protons and neutrons in the nucleus of an atom. The symbol for this number is a

Question 7

What are electrons and what do they do

Answer 7

They are the particles surrounding the nucleus of the atom. They are subatomic particles that move very fast around the nucleus
They move in orbital paths called shells

Question 8

What are groups in periodic table

Answer 8

Vertical columns consisting of elements with same amount of valence electrons, giving them similar chemical properties.

Question 9

What are periods in periodic table

Answer 9

Horizontal rows in periodic table

Question 10

What are isotopes

Answer 10

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

Question 11

What is the symbol of an isotope

Answer 11

The symbol for an isotope is the chemical symbol (or word) followed by a dash and then the mass number.

Question 12

What are the types of isotopes

Answer 12

Isotopes can be divided into two categories: radioactive and non-radioactive

Question 13

What are radioactive isotopes

Answer 13

Radioactive isotopes (radioisotopes) are unstable due to the imbalance of neutrons and protons, which causes the nucleus to decay over time through nuclear fission and emit radiation. Though they have many industrial and medical uses.

Question 14

What are non - radioactive isotopes

Answer 14

Non-radioactive isotopes are stable atoms which really only differ in their mass.

Question 15

Uses of radioactive isotopes

Answer 15

Radioactive isotopes emit radiation that can kill cells so they are used to treat cancer.
And Radioactive dating uses the carbon-14 isotope to extract carbon-containing materials such as organic matter, rocks and other artefacts.

Question 16

What is nuclear fission

Answer 16

It’s a nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy

Question 17

Is radioactive decay a nuclear process or chemical reaction

Answer 17

It’s a nuclear process

Question 18

What are the ways of representing the structure of the atom

Answer 18

We can represent the structure of the atom in two ways: using diagrams called electron shell diagrams or by writing out a special notation called the electronic configuration

Question 19

What shell of the atom has the most energy

Answer 19

The outer shell has the most energy as the further away from the nucleus the more energy the shell has

Question 20

What are the noble gases

Answer 20

They are unreactive all having full outer shells and are thus very stable with the exception of helium still having a full outer shell but only two as the smallest shell only has two compared to eight

Question 21

What’s a compound

Answer 21

A pure substance made up of two or more elements chemically combined.
Compounds cannot be separated into their elements by an physical means
E.g copper sulphate and calcium carbonate

Question 22

What is a mixture

Answer 22

A combination of two or more substances (elements and/or compounds) that are not chemically combined
Mixtures can be separated by physical methods such as filtration or evaporation.
E.g sand and water

Question 23

What are metalloids/semimetals

Answer 23

Most elements are metals and a small number of elements display properties of both metal and acid. These elements are called metalloids or semimetals

Question 24

What are the properties of metal

Answer 24

Conduct heat and electricity
Are malleable and ductile (can be hammered and pulled into different shapes)
Tend to be lustrous (shiny)
Have high density and usually have high melting points
Form positive ions through electron loss
Form basic/base oxides

Question 25

What are the properties of non metals

Answer 25

Do not conduct heat and electricity Are brittle and delicate when solid and easily break up Tend to be dull and nonreflective Have low density and low melting points (many are gases at room temperature) Form negative ions through electron gain (except for hydrogen) Form acidic oxides

Question 26

What are alloys

Answer 26

Alloys are mixtures of metals, where the metals are mixed together but are not chemically combined. Though they can also be mixed with non metals such as carbon.

Question 27

Why are alloys mostly harder than normal metals

Answer 27

Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms This makes it more difficult for the layers to slide over each other, so they are usually much harder than the pure metal

Question 28

What is an ion

Answer 28

An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons

Question 29

What holds ionic compounds together

Answer 29

The positive and negative charges are held together by the strong electrostatic forces of attraction between opposite forces. This is what holds ionic compounds together

Question 30

What is a lattice structure

Answer 30

Lattice structure refers to the arrangement of the atoms of a substance in 3D space In lattice structures, the atoms are arranged in an ordered and repeating fashion The lattices formed by ionic compounds consist of a regular arrangement of alternating positive and negative ions E.g diamond

Question 31

What are covalent bonds

Answer 31

compounds that are formed when electrons are shared between atoms Only non-metal elements participate in covalent bonding

Question 32

What are the properties of ionic compound

Answer 32

Have high melting and boiling points so ionic compounds are usually solid at room temperature Not volatile so they don’t evaporate easily Usually water-soluble as both ionic compounds and water are polar Conduct electricity in molten state or in solution as they have ions that can move and carry a charge

Question 33

What are the properties of covalent compounds

Answer 33

Have low melting and boiling points so covalent compounds are usually liquids or gases at room temperature Usually volatile which is why many covalent organic compounds have distinct aromas Usually not water-soluble as covalent compounds tend to be nonpolar but can dissolve in organic solvents Cannot conduct electricity as all electrons are involved in bonding so there are no free electrons or ions to carry the charge

Question 34

What is non polar and polar

Answer 34

Polar refers to the distribution of electrons in an atom not sharing electrons that’s why covalent bonding is non polar whale ionic bonding is polar

Question 35

Melting points and Boiling points of covalent and ionic compounds

Answer 35

Covalent compounds have weaker intermolecular bonds. It is these weak intermolecular forces that break, not the strong covalent bonds Less energy is needed to break the molecules apart, so they have lower m.p. and b.p. than ionic compounds

Question 36

What are allotropes

Answer 36

Different atomic or molecular arrangements of the same element in the same physical state. E.g diamond and graphite are allotropes of carbon which are giant covalent structures

Question 37

What are giant covalent structures

Answer 37

``` This class of substances contains a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds forming a giant lattice structure. Giant covalent structures have high melting and boiling points because of their strong covalent bonds. Large amounts of heat energy are needed to overcome these forces and break down bonds ```

Question 38

What are the uses of giant covalent structures

Answer 38

Diamond is used for jewellery as it does noir conduct electricity is the hardest substance in the world and one off the best looking in the world. Graphite can conduct electricity so Graphite is used in pencils and as an industrial lubricant, in engines and in locks It is also used to make non-reactive electrodes for electrolysis as it’s conductive

Question 39

What has intermolecular bonds got to do with conductivity

Answer 39

If structures have got weaker intermolecular bounds it’s known that they conduct electricity more as the electrons within them move more freely then when the intermolecular bonds are strong.

Question 40

What happens in a metal lattice

Answer 40

Within the metal lattice, atoms lose their valence electrons and become positively charged The valence electrons no longer belong to any metal atom and are said to be delocalised They move freely between the positive metal ions like a sea of electrons

Question 41

Why are metallic bonds strong

Answer 41

Metallic bonds are strong and are a result of the attraction between the positive metal ions and the negatively charged delocalised electrons

Question 42

What does malleable and ductile mean

Answer 42

They are layers of positive ions that can slide over one another and take up different positions Metallic bonding is not disrupted as the valence electrons do not belong to any particular metal atom so the delocalised electrons will move with them. They can be hammered and bent into different shapes without breaking