Chemistry is the study of
matter
Matter is
anything that takes up space
A chemical change is
a chemical reaction - substances are used up and others are formed in their place
An example of chemical change is
propane gas burning in the air - propane and oxygen are converted to carbon dioxide and water as they burn
A physical change is
when matter doesn’t lose its identity - a common physical change is a change of state
An example of a physical change is
ice melting. Ice is solid water, when it melts it is liquid water. It remains H20, there has been no chemical reaction - it is simply a change in state (the molecule still contains two hydrogen atoms and one oxygen atom)
The three states of matter are
solid, liquid and gas
Solid state
- particles are close together and there are strong interactions between the particles
- the movement of particles is very slow
- there is definite shape and volume
examples - ice, salt, iron
Liquid state
- particles are close together but not as close as a solid
- not fixed like a solid but it is random
- strong but not as strong as a solid
- takes the shape of the container
- has no definite shape but a definite volume
examples - water, oil, vinegar
Gas state
- particles are loosely packed and very far apart from each other
- gaseous particles don’t have any interactions
- expands to fill the container it is put into
- has no definite shape or volume
examples - water vapour and air
The difference between a mixture and a pure substance is that
a pure substance can not be further purified whereas a mixture is a combination of two of more pure substances
An element is
a substance that consists of identical atoms.
examples - carbon, hydrogen, iron
An element can not be subdivided by chemical or physical means. Elements are all the things that are found on the periodic table
How many elements have been identified
166 - of these 88 occur in nature the others have been made by chemists and physicists.
Each element is abbreviated by
a symbol which consists of one or two letters
The first letter of the chemical symbol is always a
capital
The second letter of the chemical symbol
if there is one is not a capital
The chemical symbol for hydrogen (1)
H
The chemical symbol for helium (2)
He
The chemical symbol for lithium (3)
Li
The chemical symbol for beryllium (4)
Be
The chemical symbol for boron (5)
B
The chemical symbol for carbon (6)
C
The chemical symbol for nitrogen (7)
N
The chemical symbol for oxygen (8)
O
The chemical symbol for fluorine (9)
F
The chemical symbol for neon (10)
Ne
The chemical symbol for sodium (11)
Na
The chemical symbol for magnesium (12)
Mg
The chemical symbol for aluminium (13)
Al
The chemical symbol for silicon (14)
Si
The chemical symbol for phosphorus (15)
P
The chemical symbol for sulfur (16)
S
The chemical symbol for chlorine (17)
Cl
The chemical symbol for argon (18)
Ar
The chemical symbol for potassium (19)
K
The chemical symbol for calcium (20)
Ca
The chemical symbol for gold (79)
Au
The chemical symbol for silver (47)
Ag
The chemical symbol for lead (82)
Pb
A compound is
a pure substance made up of two or more elements in a FIXED RATIO mass.
Compounds include - sodium chloride, water, glucose
The formula of a compound tells us the rations of its constituent elements and identified each element by its atomic symbol.
NACL (sodium chloride = 1 sodium atom + 1 chlorine atom)
NACL
sodium chloride = 1 sodium atom + 1 chlorine atom
H20 (numbers should be subscript)
the 2 is subscript which indicates there is a fixed ratio of 2 hydrogen atoms (H) for 1 oxygen atom (O)
C6H12O6 (numbers should be subscript)
6 carbon (C) 12 hydrogen (H) 6 oxygen (O)
A heterogeneous mixture is a
non uniform composition
examples:
- noodle soup (noodles in water)
- blood (liquid with suspended particles which are red blood cells)
- muddy water - mud particles floating in water
a homogenous mixture is a
uniform composition
examples:
- water and salt (uniform composition)
- sea water (you don’t see the salt and the water)
three points central to Dalton’s atomic theory
1) all matter is composed of tiny particles
2) compounds are formed by the chemical combination or two or more different kinds of atoms
3) a molecule is a tightly bound combination of two or more atoms that act as a single unit
The law of conservation of mass
in ordinary chemical reactions, no element disappears or is changed into an atom of another element.
Matter can neither be created or destroyed. A chemical reaction just changes the attachments but does not destroy the atoms themselves.
example carbon monoxide (C+O) + lead oxide (Pb+O) = carbon dioxide (O+C+O) + lead (Pb)
what is the difference between a monoatomic, diatomic and polyatomic molecule?
monoatomic elements - single atoms (mono means one) examples helium (He) and neon (Ne)
diatomic elements - two atoms (di means two)
examples - H2, N2, O2, F2 (numbers should be subscript)
polyatomic - have three or more atoms per molecule (poly means many)
examples - O3, P4, S8 (numbers should be subscript)
The three subatomic particles and their charges are:
Protons: +1 charge
Electrons: -1 charge
Neutrons: 0 charge
diagram of the atom showing the protons, neutrons and electrons
insert diagram from notes here
The atomic number is
the number of protons in the nucleus of the atom
Isotopes are
atoms with the same number of protons but a different number of neutrons
- Carbon-12 has 6 protons and 6 neutrons
- Carbon-13 has 6 protons and 7 neutrons
- Carbon-14 has 6 protons and 8 neutrons
Most elements on earth are a mixture of isotopes
(isotopes are similar to identical twins that have a different mass)
Mass number is
the sum of the number of protons in the nucleus of an atom
Atomic weight is
the weighted average of the masses (in amu) of the naturally occurring isotopes of an element
Periods in the periodic table are arranged in
horizontal rows
Groups in the periodic table are arranged in
vertical rows
Elements in groups have similar
recurring sets of properties
List two properties of non-metals
- lie on the right side of the periodic table (except hydrogen)
- in chemical reactions they tend to accept electrons
- dull, not shiny
- they are brittle and will shatter if hit with a hammer
List two properties of metals
- are solid at room temperature (except mercury)
- shiny
- conduct electricity
- ductile and malleable
List two properties of metalloids
- share the properties of metals and non-metals
- there are 6 elements classed as metalloids (boron, silicon, germanium, arsenic, antimony, and tellurium
- example, antimony is shiny like a metal but if you hit it with a hammer it will shatter. It is a poor conductor of electricity, it has a melting point so it shares the properties of a metal and non metal.
where are alkali metals found on the periodic table
in group 1a
where are alkaline earth metals found on the periodic table
in group 2a
where are transition metals found on the periodic table
in the section containing all the b elements (also called the d block)
where are halogens found on the periodic table
in group 7a
where are noble gases found on the periodic table
in group 8a
where are lanthanide metals found on the periodic table
directly underneath the main body of the periodic table - elements 57 through to 71
where are actinide metals found on the periodic table
underneath the main body of the periodic table, the second row contains the actinide metals, elements 89 through to 103
the electron configuration shows
the arrangement of electrons in the extranuclear space
the ground state electron configuration is the
lowest energy state of an atom
all group 1A elements have how many valance electrons in their outer shell
1
all group 8A elements have how many valance electrons in their outer shell
all 8A elements have a full complement of electrons in their outer shell as they are all stable elements
electron configuration
1s2
2s2, 2p6,
3s2, 3p6,
4s2, 3d10, 4p6