Chemical bonding Flashcards
what are the 3 types of chemical bonding
ionic, covalent, metallic
what is ionic bonding
the attraction between oppositely charged ions or metals and non- metals
what is covalent bonding
covalent bonding involves 2 non-metal atoms sharing one or more pairs of electrons
- positively charged nuclei are attracted to the shared pair of electrons by electrostatic forces, making these bonds very strong
what is metallic bonding
the attraction between positively charged ions aand negatively charged delocalized electrons
where does metallic bonding take place
in mixtures of metals and alloys
Describe cations
-cations are positive ions
-these are created when an atom loses electrons
-the metals in group 1 and 2 can easily lose electrons to be cations
describe anions
-anions are negatively charged ions
-created when an atom gains electrons
-The non-metals in Group 7 are most likely to gain electrons to fill up their electron shell and become negatively charged.
what are ionic lattices
giant structures that are held together by strong electrostatic forces between the positive and negative ions
what are ions
charged particles
why do atoms want to gain a full outer shell
so that they become stable
advantages and disadvantages of dot cross diagram
advantages
- useful in showing how ionic compounds are formed, how the electrons move
disadvantages
- they don’t show the size of the ions, the structure of the compound or the way the ions are arranged
- doesnt show the forces between the ions
properties of ionic compounds
- very high melting points because of the strong electrostatic forces in between the ions, a lot of thermal energy required to break
- when they’re solid, cannot conduct electricity, can only conduct electricity in molten form or dissolved in water, when they are in these forms, the ions are free to move and carry charge
advantages and disadvantages of ball stick diagrams
advantages
- shows the regular pattern of an ionic crystal
- shows how all the ions are arranged
- suggests that the crystal extends beyond whats shown in the diagram
disadvantages
- we can’t see the forces in between the ions
- not to scale
when does covalent bonding happen
between two non metals e.g H2O or between non-metal elements like Mg2
what are simple molecular substances
substances made up of molecules containing a few atoms joined together by covalent bonds
common simple molecular substances that I need to know
H2
CL2
O2
N2
H2O
CH4
properties of simple molecular substances
- atoms within the molecules held together by very strong covalent bonds
- the forces of attraction between the molecules are very weak
- to melt a simple molecular substance, only need to break weak intermolecular bonds, melting and boiling points very low as the molecules are easily parted
- as molecules get bigger, strength of intermolecular
increases, therefore melting and boiling points increase - they don’t conduct electricity as they aren’t charged, so there are no free electrons or ions
how does metallic bonding work
- involves delocalized electrons
- the electrons in the outer shells of metal atoms are delocalized ( free to move around ) , there are strong electrostatic forces between the positive ion and shared electrons.
- these forces of attraction hold the atoms together in a regular structure
examples of metallic bonding uses
- in metallic elements
- in metal alloys
properties of metals
- strong
- high melting and boiling points
- most are malleable
- most are solid at room temp
why do we use alloys rather than pure metals
- pure metals are often too soft, mixed with other metals to give them different properties like hardness
- mixing elements with pure metals will distort the layers of the metal atoms, making it harder for the metal atoms to slide over each other, increasing hardness again
what are ionic compounds
a giant structure of ions
Why are metals good conductors
because the delocalized electron in the metal carry electrical charge through the metal, energy in transferred by the delocalized electrons
why are metals solid at room temp
because the electrostatic forces between the metal atoms and delocalized electron are very strong, needs a lot of energy to break
why are metals malleable ( able to be bent into other shapes etc)
because the layers of atoms in a metal can slide over each other
what does the energy needed to change state depends on
the strength of the forces between the particles of the substance.
what are some limitations of particle theory diagrams
- particles are not spheres,
- particles are not solid or inelastic
- the model doesnt show the forces between the particles, so theres no way of knowing how strong they are
why do elements react
- to achieve a full outer shell
- to achieve the electronic structure of a noble gas
