Unit 1 - Chemical Bonding, atoms Ions and balancing equations T2

Question 1

Atoms

Answer 1

Everything in the world is made up of atoms. The structure of the atom is what gives an element its chemical and physical properties.

Question 2

Atoms build up

Answer 2

Electrons - negatively charged particles that spin around the positive centre of an atom in circles called energy levels. Their mass is so small that it is nearly zero.
􏰀 Protons
Positively charged particles that are contained in the nucleus of the atom (the centre) they have a mass of 1 amu (atomic mass unit).
Neutrons
Particles with no charge that are also contained in the nucleus of the atom. They also have a mass of 1 amu.

Question 3

Arrangement of periodic table.

Answer 3

Arranged in order of atomic number, horizontal rows are called periods and the vertical columns are called groups.
Elements with similar chemical properties are in the same group, and have the same no. of outside electrons.
Group 1 - alkali metals
Group 2 - alkali earth metals
Group 7 - halogens
Group 8 - noble gases.

Question 4

Properties of main groups of elements

Answer 4

Group 1, alkali metals - soft metals with low densities that react rapidly with water, producing an alkaline solution and hydrogen gas.
Group 2, alkali earth metals - similar to group 1, slightly less reactive, hardened and denser than group 1.
The elements in group 7 are known as halogens. Fluorine and chlorine are gases. Bromine is one of only two liquid elements. Iodine is solid. They exist as diatomic molecules - they have two atoms in each molecule. As you go down the group the halogens become less reactive.
The elements in group 0 are known as noble gases. They are very unreactive and exist as individual atoms (monatomic).

Question 5

Atomic numbers

Answer 5

Each element has its own atomic number. It tells you how many protons there are in the element . Since atoms are neutral they must have the same number of protons as electrons.

Question 6

Electron arrangement

Answer 6

All electrons are arranged into energy levels. First energy level can hold two electrons, with the others being able to hold 8 (only true for first 20 elements)

Question 7

Mass number

Answer 7

Mass number is protons + neutrons.

Question 8

Isotopes

Answer 8

Atoms with the same atomic number but differing mass numbers.
This means that they will have different number of neutrons.

Question 9

Relative atomic mass

Answer 9

Elements which form isotopes have relative atomic mass (RAM)
RAM of each element shown in the data book is calculated from the masses of all the isotopes of an element taking into account the percentage proportion of each. You can tell which isotope is more abundant if it is closer to the RAM.

Question 10

Covalent bond

Answer 10

Shared pair of electrons between non metal elements. Aim is to give one another a full outer shell of electrons so that it is stable. Happens when two positive nuclei from different atoms are held together by their common attraction for the shared pair of electrons between them. Covalent bonds are strong bonds

Question 11

Diatomic molecules

Answer 11

Iodine, Bromine, Chlorine, Fluorine, Oxygen, Nitrogen and Hydrogen.
Gen - u - ine.

Question 12

Shape of molecules - tetrahedral.

Answer 12

Tetrahedral - four shared pairs of electrons, drawn with two lines, one dotted line and a triangle coming from the atom with valency of 4 to other atoms pointing in different directions. Example methane.
CH4

Question 13

Valency

Answer 13

The no. of electrons an atom can share.
Group 1 - V1
Group 2 - V2
Group 3 - V3
Group 4 - V4
Group 5 - V3
Group 6 - V2
Group 7  - V1
Group 8 - V0

Question 14

Shape of molecules - Trigonal pyramidal

Answer 14

3 shared pair of electrons, drawn with one straight line, one dotted line and one triangle coming from the V3 atom to the other atoms. Example ammonia
NH3

Question 15

Shape of molecules - angular

Answer 15

2 shared pairs of electrons. Drawn with two straight lines coming from the V2 atom to the other atoms. Example water H20

Question 16

Shape of molecules double bond

Answer 16

When double or even triple bonds are shared draw bond with two lines rather than one.

Question 17

Covalent Network

Answer 17

Covalent substances that are solids with high melting points have much larger molecules. A covalent network structure consists of a giant 3 dimensional lattice of covalently bonded atoms.
Examples of covalent networks are boron, carbon and silicon.
Carbon forms two structures diamond and graphite. Diamond is tetrahedral, graphite has a layered planar structure.

Question 18

Ionic bonding

Answer 18

Ionic bonds are formed between a metal and a non metal for example sodium chloride. An atom of metal will lose an electron and form a positive ion. Metals form positive ions because they lose electrons to become stable. A non metal atom will gain an electron and form a positive ion
Ionic bond is the electrostatic force of attraction between a positively charged metal and a negatively charged ion.

Question 19

Ionic compounds structure

Answer 19

Form a lattice structure, regular repeating arrangement of metal and non metal ions which creates compounds which conduct when molten or in solution but never when solid P. Can conduct as in those cases ions are free to move. Have high melting and boiling points due to the strong elctrostatic forces between them.
Dissolve in water easily.

Question 20

Metallic bonding

Answer 20

In metallic npbonding the outer electrons are delocalised (free to move) this produces an electrostatic force of attraction between the positively charged metal ions and the negatively charged delocalised electrons.They generally have high melting points and boiling points however there is a great range in these melting and boiling points between metals. They conduct electricity due to their delocalised electrons which allow the flow of an electric charge through the metallic lattice. They can also be malleable and ductile.

Question 21

Malleable

Answer 21

(of a metal or other material) able to be hammered or pressed into shape without breaking or cracking.

Question 22

Ductile

Answer 22

(of a metal) able to be drawn out into a thin wire.

Question 23

Electrolysis

Answer 23

Breaking up of an ionic solution using electricity..

Question 24

Set up of electrolysis

Answer 24

Breaker containing ionic solution, has a D. C suppl with a negatively charged electrode and a positively charged electrode in it.

Question 25

Electrolysis breakup

Answer 25

Solution is broken up because electricity is passed through the solution. Positive metal ions are attracted to the negative electrode, their receiving electrons to form normal metal. Negatively charged non metals are attracted to the positive electrode, there the ions lose extra electrons to form normal non metal. Equation for metal looks like ionic formula for metal + electrons needed ——> normal metal. Non metal ionic formula——> normal non metal + electrons given away.

Question 26

Ions

Answer 26

Atoms with same protons but different number of electrons.

Question 27

Chemical formulae

Answer 27

Shows the number of atoms of each element in the compound.

Question 28

Prefixes

Answer 28

``` Mono - one Di - two Tri - three Tetra - four Penta - five Hexa - six ```

Question 29

Figuring out formula

Answer 29

Step one - write down the symbols of both the elements involved. Be careful of group ions like phosphate - find in data booklet. Step two - beneath each symbol, write its valency. Step three - swap the valencies over. Step four - if the valencies can be simplified, divide them both by the smaller of the two numbers. If one of the numbers is already one, then they cannot be divided and simplified any further. Step five - write the formula. If group ion is there put it in brackets - (NO3)

Question 30

Formula Using Roman Numerals

Answer 30

Some elements, particularly the transition metals, do not always have the same valency in their different compounds. The valency of these elements is usually given in roman numerals inside brackets.

Question 31

Ionic Formula - charges need

Answer 31

Initially we work out the chemical formula of the compound using the SVSDF method. 2. Using the valency of each element you add the charge of that element to the top right of the symbol. A metal is always positively charged and the non-metal is negatively charged.

Question 32

Balancing equations

Answer 32

1. Write out unbalanced equation. 2. Write all elements in equation under = sign and write no. of each on their represented side. 3. Multiply compounds / elements to make equal and always add on to no. when a change has been made. 4. Once equal rewrite equation.