Download atomic structure revision and questions 08

Year 10 Science Revision Booklet
ATOMIC STRUCTURE REVISION AND QUESTIONS 2015
Key words:
element
nucleus
molecule
neutron
atom
proton
mass number
electron
energy level
ion
formula
compound
atomic number
mass number
Key definitions to learn:
Element
Atom
Molecule
Compound
Atomic number
Mass number
An element consists of one type of atom.
An atom is made of protons and neutrons in a nucleus surrounded
by electrons which orbit the nucleus in energy levels (shells). An
atom is the smallest particle that can take part in a chemical
reaction without be permanently changed
Group of non-metal atoms bonded (joined) together e.g. H2 or H2O
Two or more different elements bonded together e.g.. NaCl or H2O
The number of protons in the nucleus of an atom.
The number of protons added to the number of neutrons in the
nucleus
Key Learning Points:
What is an element?
An element contains one type of atom.
How do we represent elements?
An element is represented by a symbol. The symbols are shown on the Periodic
Table.
The metals are on the left side and non-metals on the right.
e.g. S = sulphur, Na = sodium, C = carbon, Cu = copper,
Cl = chlorine, Ca = calcium
Some elements exist in pairs as molecules and are represented by a formula e.g. F2,
Cl2, Br2, I2, H2, N2 and O2
Molecules are made of 2 or more non-metal atoms joined together.
What is the structure of an atom like?
Atoms consist of a positively charged nucleus with negatively charged electrons
orbiting the nucleus. Inside the nucleus there are positively charged particles called
protons and particles called neutrons, which are neutral.
x
proton
Model of an atom: Draw in the protons and neutrons
Be able to
There are 2 electrons
neutron
label it!
electron in an energy level
x
nucleus
Year 10 Science Revision Booklet
Particles in an
atom
Proton
Neutron
Electron
Relative
mass
1
1
1/1836
negligible
Relative
charge
+1
0
-1
Where in the atom is it
found?
nucleus
nucleus
orbiting in energy levels
What does the number of protons tell us?
 Atoms of different elements have a specific number of protons in their nucleus.
 The number of protons inside an atom is called the proton number or atomic
number
 So each element has its own proton number ie. atomic number.
 The proton number is the smaller number next to the element on the Periodic
Table.
 All atoms of Na have a proton number of 11 i.e. they have 11 protons
11Na
How can we tell how many neutrons there are in a nucleus?
The number of protons + the number of neutrons is called the mass number.
To find the number of neutrons in an atom of an element:
No. of neutrons = mass no. – no. of protons
23
The mass number is the larger number next to the element on the Periodic Table
How can we tell how many electrons there are in an atom?
The number of electrons is always equal to the number of protons if the atom is
neutral.
No. of protons = no. of electrons
How are the electrons arranged in an atom?
Electrons are arranged in energy levels around the nucleus of an atom
An atom can hold a maximum number of electrons in each energy level
1st energy level = 2 electrons
2nd energy level = 8 electrons
3rd energy level = 8 electrons
Atom
Atomic Number (Proton
Number) and Symbol
Electron Arrangement
Electron
Diagram
Electron diagrams show the arrangement of
electrons in energy levels inside the atom.
Beryllium
4Be
2,2
Carbon
6C
Aluminium
13Al
Na
Year 10 Science Revision Booklet
Atom
Atomic Number (Proton
Number) and Symbol
Electron Arrangement
Electron
Diagram
Fluorine
9F
Oxygen
8O
Chlorine
17Cl
2,7
Calculating Numbers of Sub-atomic Particles – protons, neutrons and electrons
Element
Symbol Mass
Atomic
number No.
No. of
No. of
No. of
Electron
protons neutrons electrons arrangement
(Proton
number)
Lithium
Neon
Magnesium
Sodium
Potassium
Fluorine
7
20
23
39
3
10
19
9
3
10
12
11
12
2,8
9
10
11
19
What happens when elements react?
Elements can react to form ions. Ions are charged atoms.
o Metals form positive ions e.g. Na+
o Non-metals form negative ions e.g. ClThe oppositely charged ions join together to form a compound.
How are electrons arranged in ions?
Metal atoms lose electrons to form ions:
Metal atom → Metal ion + electron lost
Electron
arrangement
Electron diagram
Atom = Na
2,8,1
e.g. Na → Na+ + ē
Ion = Na+
[2,8]+
Year 10 Science Revision Booklet
Non-metal atoms gain electrons to form ions:
Non-metal atom + electron gained → Non-metal ion e.g. e.g. Cl + ē → ClIon = Cl[2,8,8]-
Atom = Cl
2,8,7
Electron
arrangement
Electron diagram
What is a Compound?
 A compound contains 2 or more elements bonded together.
E.g. Sodium chloride contains sodium and chlorine.
 The properties of a compound are different to the properties of the
elements it is made from.
 A compound is represented by its formula. E.g. sodium chloride has
the formula NaCl. The formula shows how many of each type of atom
are in the compound.
Representing Compounds by Formulae
Chemical name Chemical
formula
Elements
present
Number of
atoms of each
element
Total number
of atoms in
the formula
Sulfuric acid
(sulphuric acid)
H2SO4
Hydrogen
Sulphur
Oxygen
2xH
1xS
4xO
7
Magnesium oxide
MgO
Sodium hydroxide
NaOH
Magnesium
fluoride
MgF2
Sodium nitrate
NaNO3
Ammonium
nitrate
(NH4)2 SO4
Calcium
hydroxide
Ca(OH)2
Year 10 Science Revision Booklet
Naming Compounds
You should learn some common compound names - e.g.
H2SO4 = sulphuric acid
H2O = water
NaOH = sodium hydroxide
HCl = hydrochloric acid
CO2 = carbon dioxide
You can work out the names of others.
 If there is a metal in the formula, name it first.
e.g CaO is calcium oxide
 The non-metal part changes slightly:
The symbol O is oxygen. In a compound it becomes oxide
The symbol Cl is chlorine. In a compound it becomes chloride.
The symbol F is fluorine. In a compound it becomes fluoride.
The symbol Br is bromine. In a compound it becomes bromide.
The symbol I is iodine. In a compound it becomes iodide.
The symbol S is sulphur or sulfur. In a compound it becomes sulphide or
sulfide.
e.g. NaS = sodium sulfide
Some groups of atoms have a special name i.e
SO4 is sulphate or sulfate
NO3 is nitrate
HCO3 is hydrogencarbonate
CO3 is carbonate
Formula
KCl
FeO
CuCO3
MgSO4
Name
Potassium chloride
Formula
NaF
CuS
NaNO3
Zn(OH)2
OH is hydroxide
Name
How do we write Formulae for Compounds?
To be able to write the formula for compounds we need to know the charges on the
ions that are bonding. See Table of Ions on the back of the Periodic Table.
The positive metal ions and negative non-metal ions combine in a certain ratio so that
a neutral compound forms. e.g. Ca2+ can combine with 2 Cl- ions to form CaCl2
Combining method:
Ca2+
Cl(2+) x 1 ( 1-) x2
2+ =
2Ca Cl2
Using the crossover method:
Using the lego block method
Ca2+ Cl-
Ca2+
Cl-
Cl-
Ca1 Cl2
State the ratio of each ion in the compound and name the compound.
Compound Name
Formula
MgSO4
CaF2
Na2O
KNO3
Ca(OH)2
Ratio of ions
1Mg2+ : 1SO421Ca2+ : 2F-
Year 10 Science Revision Booklet
Write formulae for:
Compound
Calcium chloride
Lead oxide
Sodium sulfide
Ions
Ca2+ ClPb2+ O2Na+ S2-
Formula
Compound
Iron hydroxide
Sodium sulfate
Lead oxide
Ions
Fe3+ OHNa+ SO42Pb2+ O2-
Formula
Website URL for revision:
http://www.bbc.co.uk/schools/gcsebitesize/chemistry/classifyingmaterials/atomic_structure1rev1.
shtml
Draw a mindmap for this unit:
Add to it, as you develop your learning.
Atoms
Well done you have completed another revision unit.
Now reflect on how you can improve further:
Which aspects of the unit do I need to revise more carefully?
Which aspects of the unit do I need help with?
How will I seek this help?
Year 10 Science Revision Booklet