Chemical Bonding Flashcards
What is a compound?
2 or more different elements chemically combined
How are atoms held together?
chemical bonds
describe noble gases
contain 8 elements on outer shell and are generally unreactive
what are the uses of helium
airships and balloons
uses of argon
Used in lightbulbs (normal light bulbs) to stop imploding
what is the octet rule
in forming compounds, atoms tend to achieve the electron configuration of a noble gas(8 electrons)
what are the limitations of the octet rule
hydrogen, lithium, transition elements
what is a valency
it is the no. of bonds an atom makes when it reacts
what is a transition metal
it is one that forms at least one ion with a particularly filled sublevel
facts about transition metals
they have variable valancy
form coloured compounds
used as catalysts
name 2 types of bonding
ionic,convalant
what is an ion
a charged atom/groups of atoms
what is the charge of a cation
positive
what is the charge of a anion
negative
define ionic bonds
the attraction between oppositely charged ions in a compound
why do ionic substances form substances
positive ions attract negative ions in all direcions
what are the characteristics of ionic substances
- strong forces between ions means its very hard to –break up the lattice structure
- can conduct electricity when solid
- high melting/boiling points
- most dissolve in water
- solid at room temp
examples of everyday ionic substances
table salt-Sodium Chloride (NaCl)
fluoridation in water-SodiumFlouride(NaF)
When is a covalent bond formed?
when electrons are shared between atoms
what are bonding pairs
shared electron pairs that form covalent bonds
What are lone pairs?
electron pairs not involved in bonding
How is a sigma bond formed?
formed by the head overlap of two orbitals (can be s/p orbitals)
how is a pi bond formed
formed by sideways overlap of p-orbitals
which is stronger sigma vs pi bonds
sigma bonds are stronger due to the fact that there is more overlap between orbitals
what are the characteristics of ionic bonds
- transfer of electrons
- ions formed
- high melting/boiling point
- usually solid at room temp
- conducts electricity when molten
what are the characteristics of covalent bonds
- sharing electrons
- covalent bonds formed
- low melting/boiling points
- liquid/gaseous at room temp
- deosnt conduct electricity
what is In a single bond
one sigma
what is in a double bond
one sigma, one pi
what is in a triple bond
one sigma, two pi
How are molecules formed?
Covalent bonds between two or more atoms.
How is the shape of a molecule determined?
the arrangement of atoms
what theory is used to figure up the arrangement of molecules
VSEPR- valance shell electron pair repulsion theory
describe why the shape of lone and bonding pairs are disstorted(explain the basis for electron pair repulsion pair theory(i think))oooop
- lone pair electrons are closer to the nucleus
- due to this it they are closer together
- collective nuclear charge pushes the bonding pairs further apart
decreasing the bond angle+distorts the shape
electrons in bonding pairs repel each other and want to be as far away as possible
no. of bonding pairs around the central atom and angle of a linear molecule
2 atoms and 180 degrees
no. of bonding pairs around the central atom and angle of a trigonal planar atom
3 atoms and 120 degrees
no. of bonding pairs around the central atom and angle of a tetrehedral atom
4 atoms and 109.5 degrees
what are lone pairs
Paired electrons that are not shared
what is a molecule, no of bonding pairs,no of lone pairs, bod angle of a pyramidal molecule
NH3, 3, 1 ,107 degrees
what is a molecule, no of bonding pairs,no of lone pairs, bod angle of a V-Shaped molecule
H20, 2 , 2, 104.5 Degrees
What are non-polar covalent bonds?
equal sharing of electrons
What are polar covalent bonds?
unequal sharing of electrons
Define Elecronegativity
its the relative attraction an atom has for a shared pair of electrons in a single covelent bond
what are the trends in the periodic table in terms of electromagnetically
Increase across the table=increase in nuclear charges/decreased atomic radius
Decrease down the table=screening/increase atomic radius
how do you predict the type of bond an atom has
check the electronegativity of the atoms involved
calculate the difference in electronegativity
what is the bond type of atoms with the electronegativity of non-polar covelant bonds
0-0.4 ex-H2,O2
what is the bond type of atoms with the electronegativity of polar covelant bonds
0.41-1.7 example-H20
what is the bond type of atoms with the electronegativity of Ionic bonds
greater than 1.7 example-NaCl
a molecule that has polar bonds can be non-polar overall if its one of the following shapes
linear,trigonal planar, tetrahedral
What is intramolecular force?
force within a molecule
What is intermolecular force?
force between molecules
what are the three types of molecular bonding
Van Der Waal
Dipole-Dipole
Hydrogen bonding
What are Van der Waals forces?
weak forces of attraction between temporary dipoles
What are dipole-dipole forces?
forces of attraction between negative polar of one molecule and the positive pole of another
What are hydrogen bonds?
occurs in molecules where a hydrogen atom is bonded to nitrogen,oxygen,fluorine. the hydrogen carries a positive charge and is attracted to the electronegative in another molecule
