Chemistry - structure of an atom

atomic no.

total no. of protons

atomic mass

total no. or protons and neutrons

no ion

neutural element

If two unknown elements have a different protons, are they the same or different.

Different protons always DIFFERENT ELEMENTS. No element have a version of its different amount of proton

Ion

• neutral atom, can gain or lose an electron

  eg, ion w -1

  -> becomes a negative ion with a charge of –1.

• Ion does not DESTROY protons it CANCELS the charge

What are isotopes

• Same element different mass

• because of neutrons

• reason why physical properties different even its same element

What’s the relationship with metals and their outershells?

Metals (80% of elements)

are atoms that usually have less than four electrons in outer shell

What’s the relationship with non-metals and their outershells?

Non metals usually have more than 4 electrons in outer shell

Properties of metal

• good conductors of electricity

• high melting + boiling points

• high density

  (the mass of a substance per unit volume.)

• Malleable (bendy)

• Ductile (can roll in wire)

• Lustrous (shiny)

• Solid (EXCEPT MERCURY)

• 1-3 valence electrons

• form cations (+ve) in solution

Properties of non metlas

• poor conductors of electricity

  (except carbon)

• Variable (lower than metals) melting and boiling points

• Good insulators (doesn’t easily allow heat, electricity, light, or sound to pass through it)

• Brittle

• Dull

• 4-7 valence

• Form anions (-ve) in solution

How are Elements arranged?

• due to electronic configuration

• this means their electrons are arranged in energy levels called shells

What is the rule/pattern of shells

1st shell - 2 electrons

2nd shell - 8 electrons

3rd shell - 18 electrons (8*) OCTECT RULE!!

4th shell - 32 electrons

What is the octet rule

What term is used for the electrons in the outermost shell or energy level?

valence or electrons