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Slide 1

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CHEMISTRY UNIT 2…read more

Slide 2

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· Nucleus ­ middle of the atom, protons and
neutrons, positive charged and the entire
mass is mostly from the nucleus.
· Electrons ­ move around the nucleus,
negatively charged, tiny but cover a lot of
space, the volume of their orbit determine
how big the atom is, virtually no mass, shells
around the nucleus, these shells explain the
whole of chemistry
Particle Mass Charge
Proton 1 +1
Neutron 1 0
Electron Very small -1…read more

Slide 3

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· The mass number is the total of protons and
neutrons (top half)
· The atomic number is the number of protons
(bottom half)
· Atoms of the same element all have the same
number of protons ­ so elements that are
different will always have different proton
· Number of neutrons is atomic number ­ mass
· Mass number is the relative atomic mass
· Mass number is usually double the proton
number, meaning there is usually the same
amount of protons as neutrons in a nucleus…read more

Slide 4

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· Elements are one type of atom ­ copper,
aluminium, iron, oxygen and nitrogen.
· Compounds are chemically bonded ­ two or
more elements chemically react together,
difficult to separate again, properties of a
compound are different to the element
· Isotopes are the same except for an extra
neutron or two: Isotopes are: different
atomic forms of the same element, which
have the same number of protons but a
different number of neutrons.…read more

Slide 5

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· Table of Elements ­ 100 or more elements,
elements with similar properties are in the same
column, ascending order of atomic number.
· Group 1 ­ alkali metals (reactive metals)
· Group 7 ­ halogens
· Group 0 ­ noble gases
· Elements in a group have the same number of
outer electrons (this is why they have similar
· Electron shells form the basis of all chemistry
without them there would be no chemical
reactions ­ no nothing.
· Electron arrangement determines its behaviour…read more

Slide 6

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· Electron shells rule: electrons always occupy
shells, the lowest energy levels are always
filled first, only a certain number of
electrons are allowed in each shell: 2, 8, 8,
they're better with full shells, most atoms the
outer shell is not full and this makes the atom
want to react.…read more

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