3.2- COVALENT BONDING Flashcards
What do non-metal atoms need to do to fill the space in their outer shells?
receive electrons
What does a covalent bond form between?
a pair of non-metal atoms
What do the atoms in a covalent bond do?
share some of their outer shell electrons
Why do atoms in a covalent bond share some of their outer electrons?
so that each atom has a stable noble gas arrangement
What is a covalent bond?
shared pair of electron
What is a small group of covalently bonded atoms called?
a molecule
example of a molecule from covalent bonding?
chlorine- Cl2
How many electrons does chlorine have?
17
What is the electron arrangement of chlorine?
1s2 2s2 2p6 3s2 3p5
What happens when two chlorine atoms make a chlorine molecule? (4)
two atoms share one pair of electrons
each atom now has stable noble gas arrangement
formula is Cl2
molecules neutral as no electrons have been transferred from one atom to another
How can you represent one pair of shared electrons in a covalent bond?
by a line
e.g. Cl-Cl
How are atoms with covalent bonds held together?
by electrostatic attraction between nuclei and shared electrons
How many electrons are there in a double bond?
four electrons
How many pairs of electrons do the two atoms in an oxygen molecule share?
two
What sort of bond is between the oxygen atoms in an oxygen molecule?
double bond
How can you represent the two pairs of shared electrons in a covalent bond?
with a double line, O=O
What sort of melting temperature do substances composed of molecules have?
low melting temperature
Why do substances composed of molecules have a low melting temperature?
the strong covalent bonds only BETWEEN the atoms within a molecule
only weak attraction between molecules so molecules don’t need much energy to move apart from each other
Are substances composed of molecules good conductors of electricity and why?
poor conductors of electricity as molecules neutral overall
As the molecules are neutral overall what does this mean? (hint- current)
no charged particles to carry the current
If substances composed of molecules were dissolved in water and remain as molecules, will they be able to conduct electricity and why?
no because there are no charged particles
What does a single covalent bond consist of?
a pair of electrons shared between two atoms
What is done by each atom in most covalent bonds?
each atom provides one of the electrons
What happens in some bonds? (covalent)
one atom provides both the electrons
What is it called when one atom provides both the electrons?
co-ordinate bonding or dative covalent bonding
In co-ordinate/ dative covalent bond… (2)
atom that accepts electron pair is atom that doesn’t have a filled outer main level of electrons- atom is electron-deficient
atom that’s donating electrons has a pair of electrons that’s not being used in bond, called lone pair
example of co-ordinate bonding?
ammonium ion NH4^+
What does ammonia, NH3 have? (electrons)
lone pair of electrons
What does nitrogen do in NH4^+?
nitrogen uses its lone pair of electrons to form coordinate bond with an H+ ion (bare proton with no electrons so electron deficient)
How are coordinate covalent bonds represented?
by an arrow
where does the arrow representing a coordinate covalent bond point towards?
towards the atom that’s accepting the electron pair
What does the arrow for coordinate bonding ONLY show?
only to show how the bonds was made
about the ammonium ion:
completely symmetrical and all bonds have exactly the same strength + length
What are the coordinate bonds’ strength + length in comparison to ordinary covalent bonds?
exactly the same
how is the ammonium ion bonded and does it have a charge?
covalently bonded but is a charged particle
