chemistry 2a- bonding and calculations
- Created by: shona
- Created on: 29-12-12 15:03
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- chemistry 2a- bonding and calculations
- atoms compounds and isotopes
- atoms
- contains protons neutrons and electrons
- atomic number and mass number describe the atom
- mass number
- the top number on this symbol tells you the total number of protons and neutrons
- atomic number
- the bottom number tells you the number of protons
- mass number
- the atomic number tells you how many protons there are
- atoms of the same element all have the same number of protons so atoms of different elements will have different numbers of protons
- to get the number of neutrons subtract the atomic number from the mass number
- electrons aren't counted in the mass number because their relative mass is very small
- compounds
- compounds are chemically bonded
- compounds are formed when 2 or more elements are chemically combined together
- for example carbon dioxide is a compound formed from a chemical reaction between carbon and oxygen
- it is difficult to separate the two original elements again
- isotopes
- isotopes are the same except for an extra neuron or two
- DEFINITION: ISOTOPES ARE DIFFERENT ATOMIC FORMS OF THE SAME ELEMENT WHICH HAVE THE SAME NUMBER OF PROTONS BUT A DIFFERENT NUMBER IF NEUTRON
- isotopes must have the same atomic number but different mass number
- if they have different atomic numbers they'd be different elements altogether
- carbon 12 and carbon 14 are a very popular pair of isotopes
- atoms
- ionic bonding
- atoms lose or gain electrons to form charged particles(ions) which are strongly attracted to one another( because of the attraction of opposite charges + and -)
- all the atoms on the left side of the periodic table only have one or two electrons on their outer shell so they are keen to get rid of them
- meaning they will have a full outer shel
- when they get rid of the electrons the atoms become ions instead
- now they are ions they like to join with other ions of the opposite charge and stick to it like glue
- on the right side of the periodic table the elements outer shell is nearly full so they want go gain electrons to make a full outer shell
- when they become an ion they latch on to the atom that gave them the electrom
- ionic compound have a regular lattice structure
- ionic compounds always have giant ionic lattices
- the ions form a closely packed regular lattice arrangement
- there are very strong electrostatic forces of attraction between oppositely charges ions in all directions
- ionic compounds all have similar properties
- high melting and boiling points due to the strong attractions between ions
- takes a large amount of energy to overcome this attraction
- when ionic compounds melt they are free to move and they'll carry electric current
- they dissolve easily in water
- the ions separate and are free to move in the solution so they'll carry electric current
- high melting and boiling points due to the strong attractions between ions
- ions and formula
- groups 1 and 2 and 6 and 7 are most likely to form ions
- atoms that have lost or gained electrons are ions
- ions have the electronic structure of a noble gas
- group 1 and 2 are metals they lose electrons to form a positive ion
- group 6 and 7 are non-metals they gain electrons to form negative ions
- the charge on positive ions is the same as the group number of the element
- only the elements at the opposite sides of the periodic table will form ionic compounds
- atoms compounds and isotopes
- remember to give is positive and to take is negative
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