SCIENCE CHEMISTRY (Sec3): Chpt4_Atomic Structure Flashcards
(19 cards)
types of chemical bonding [3 types]
- ionic bonding
- covalent bonding
- metallic bonding
noble gases [2pts]
- have full valence shells of electrons = noble gas electronic configurations
- are inert & exist as monoatomic gases (one atom only; already have full valence shell)
atoms bond together
to achieve stable electronic configuration of noble gases
chemical bond
a very strong force between the atoms
ionic bonding [5pts]
- involves transfer of electrons
- occurs between metals and non-metals
- metals lose electrons to form +ve ions (cations)
- non-metals gain electrons to form -ve ions (anions)
- compound containing ionic bond: ionic compound
ionic compound [3pts]
- compound containing ionic bond
- ionic compound: electrically neutral, have no net charge
- ionic compounds have giant ionic crystal lattice structures (3D structure; alternating cations & anions)
no. of electrons gained and lost
must be conserved
relationship bwt. charges and electrostatic forces of attraction and m.p. and b.p. (ionic substances)
- bigger the charges, stronger the electrostatic attraction force
- m.p. and b.p. are higher also
covalent bonding [3pts]
- sharing of electrons equally bwt. atoms of non-metals
- number of covalent bonds bwt. atoms depends on number of pairs of shared electrons
- can be single, double or triple
covalent molecules [4pts]
- most are simple molecules
- have countable number of atoms in a fixed ratio (e.g. water molecule)
- some are giant molecules
- have uncountable number of atoms in each molecule (e.g. diamond, sand)
simple covalent molecules [1pt + examples]
- attracted by weak intermolecular force bwt. each other
- examples: methane, iodine, water, carbon dioxide, ammonia
giant covalent substance
- formed by large number of atoms covalently bonded to one another
- structure consists of network of strong covalent bonds
- two giant molecular substances formed by carbon element: 1. diamond, 2. graphite
metallic bonding [6pts]
- atoms of metallic elements have tendency to lose their valence electrons
- become +ve ions
- in metals, metallic lattice consists of +ve ions surrounded by ‘sea of delocalised electrons’
- metallic bond: strong electrostatic attractive force bwt. ‘sea of electrons’ and +ve ions
- metallic bond: mutual electrostatic attractive force bwt. +vely charged ions in metal and ‘sea of delocalised electrons’
- giant metallic bonds help metals have giant metallic lattice structure in solid state
sea of delocalised electrons (metallic bonding) [1pt]
electrons from metal atoms which are free to move about bwt. +ve ions
properties of metals [7pts]
- giant metallic lattice structure of pure metal: same size atoms arranged in regular pattern & are evenly distributed throughout the solid
- regular arrangement: layers of atoms can slide over each other easily when force is applied
- makes pure metal to be soft, malleable & ductile
- have high m.p. and b.p.
- good conductors of electricity and heat: ‘sea of delocalised electrons’ free to move within giant metallic lattice (act as charge carriers)
- do not dissolve in water and in organic solvents
- corrodes easily
malleable (properties of metals)
solid can be beaten or hammered into shapes or thin sheets without breaking
ductile (properties of metals)
solid can be stretched or pulled into wires without breaking
alloy [4 pts + examples]
- mixture of metal with one or more elements
- some contain non-metals
- melt over range of temp.s
- e.g. brass (copper and zinc), stainless steel (iron, nickel, chromium), steel (iron and carbon)
properties of alloys [5pts]
- good conductor of electricity and heat
- hard and strong
- less malleable
- resistant to corrosion
- do not dissolve in water and in organic solvents
