CHEMISTRY C1.1
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- Created on: 23-03-16 18:35
Element
An element is a substance that cannot be broken down into anything simpler - they are made from just one type of atom
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Chemical symbols
Atoms of each element are represented by a chemical symbol e.g. O represents an atom of oxygen
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The periodic table
The periodic table lists all the elements. The columns are called GROUPS (number of electrons in the outer shell) and the rows are called PERIODS (number of shells).
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Metals and non-metals in the periodic table
A stepped line towards the right hand side of the table separates the metals from the non-metals. The metals are to the left of the line and about 3/4 of the elements are metals.
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Atomic number order
The elements are listed in atomic number order (atomic number = number of protons)
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Elements in the same group
They have similar chemical properties because they have the same number of electrons in the outer shell.
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Atom structure
Atoms consist of a central nucleus containing protons and neutrons which is surrounded by electrons in shells. the nucleus is tiny compared to the size of the whole atom
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Relative mass
P = 1, N = 1, E = negligible
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Charge of sub atomic particles
P = +1, N = 0, E = -1
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Atomic number
number of protons, in atoms P = E, so atoms are neutral (no charge)
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Mass number
Number of protons + number of neutrons
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Atoms of the same element
They have the same number of protons. The number of protons determines the type of atom. Atoms of different elements have different numbers of protons
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Electrons in atoms
They are arranged in shells, 1st shell = 2 E, 2nd shell = 8 E, 3rd shell = 8E. any electron arrangement with only full shells is very stable (e.g. Ar (2,8,8)
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Group 1 elements - the alkali metals
Li, Na, K, Rb and Cs. They are all highly reactive, soft metals that have similar chemical properties. When the elements react they lose one electron to gain a full outer shell. All the group 1 metals react in similar ways with water and oxygen
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Group 0 elements - the noble gases
He, Ne, Ar, Kr, Xe and Rn. They are all very unreactive gases and non-metals. They all have similar chemical properties because they all have full outer shells. This means they have no need to gain, lose or share electrons.
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Uses of noble gases
Because they are so unreactive, this can be useful. in filament lightbulbs, they are filled with Ar gas so it does not react with the metal in the hot filament wire.
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Chemical reactions - M+ NM
Electrons are transferred from M to NM atoms. This forms ions with +ve and -ve ions attracted to each other by electrostatic attraction. (e.g. sodium + chlorine --> sodium chloride
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Chemical reactions - NM + NM
Electrons are shared to form molecules (with atoms within molecules joined together by covalent bonds). (e.g. hydrogen + oxygen --> water
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Ions
Ions are electrically charged particles formed when atoms lose (+ve charge) or gain (-ve charge) electrons.
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Formation of ions
Atoms lose or gain electrons in order to form ions which have electron arrangements only with full shells (e.g. Na (2,8,1) loses one electron to form Na+ ion (2,8,0). O (2,6) gains two electrons to form O2- ion (2,8)2-
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State symbols
(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water
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Balanced equations
An equation is balanced when there is the same number of atoms of each type on both sides of the equation. An equation can only be balanced by putting numbers in front of the formulas, not changing the formula itself
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Conservation of mass
he mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.
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Other cards in this set
Card 2
Front
Atoms of each element are represented by a chemical symbol e.g. O represents an atom of oxygen
Back
Chemical symbols
Card 3
Front
The periodic table lists all the elements. The columns are called GROUPS (number of electrons in the outer shell) and the rows are called PERIODS (number of shells).
Back
Card 4
Front
A stepped line towards the right hand side of the table separates the metals from the non-metals. The metals are to the left of the line and about 3/4 of the elements are metals.
Back
Card 5
Front
The elements are listed in atomic number order (atomic number = number of protons)
Back
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