Chemical bonding

Question 1

how are ionic bonds formed?

Answer 1

when electrons are transferred between atoms to make positive or negative ions

Question 2

how are covelant bonds formed??

Answer 2

when atoms share pair of electrons

Question 3

what is electronegativity

Answer 3

is the tendency for an atom of a given chemical element to attract shared electrons when forming a chemical bond

Question 4

state the laws of electronegativity

Answer 4

=equal sharing of the electron pair gives a pure covalent bond
=unequal sharing of the electron pair gives a polar covalent bond
=transfer of electrons gives an ionic bond

Question 5

what is the electronegativity of a pure covalent bond?

Answer 5

0

Question 6

what is the electronegativity of an ionic bond?

Answer 6

bigger or equal to 2

Question 7

what is the electronegativity of a polar covalent bond?

Answer 7

0 to 1,9

Question 8

explain “atoms which make more than 4 bonds”

Answer 8

examples are sulfur and phosphorus, these elements have empty d orbitals to which electrons can move if enough energy is available in a reaction

Question 9

Multiple bonds??

Answer 9

=atoms share more than one pair of electrons to make a double or a triple bond
=atoms joined by single bonds can rotate around the bond but atoms joined by multiple bonds are fixed in a position and cannot rotate.
=O and S atoms form double bonds while C and N atoms form both double and triple bonds.

Question 10

Dative covalent bonds??

Answer 10

they are formed by overlapping of a filled orbital containing a lone pair with the empty orbital of another atom or ion.

Question 11

what is the symbol for dative covalent bonds??

Answer 11

see page 139

Question 12

Shapes of molecules

Answer 12

depends on son the number of electron pairs surrounding the central atom.
=these may be shared pairs of electrons or lone pairs
=electron pairs spread out equally in space but lone pairs take up more space than shared pairs.

Question 13

VSPER?

Answer 13

predicts that there is repulsion between pairs of electrons

lone pair -lone pair>shared pair-lone pair>shared pair -shared pair

Question 14

shape of molecule(molecules containing a single bond )

Answer 14

linear

bond angle is 180 degrees

Question 15

shape of molecule(molecules containing of 2 single bonds )

Answer 15

linear

bond angle is 180 degrees

Question 16

shape of molecule(molecules containing 3 single bonds )

Answer 16

trigonal planar

bond angle is 120 degrees

Question 17

shape of molecule(molecules containing 4 single bonds )

Answer 17

tetrahedral

bond angle is 109 degrees

Question 18

shape of molecule(molecules containing 3 single bonds and a lone pair )

Answer 18

pyramidal

bond angle is 107,5 degrees

Question 19

shape of molecule(molecules containing 2 single bonds and 2 lone pairs )

Answer 19

angular

bond angle is 105 degrees

Question 20

shape of molecule(molecules containing 5 single bonds )

Answer 20

trigonal bi-pyramid

bond angle is 120 degrees in the plane and top and bottom bond at 90 degrees to the plane

Question 21

shape of molecule(molecules containing 6 single bonds )

Answer 21

octahedral

bond angle is 90 degrees

Question 22

what are polar molecules?

Answer 22

they have one slightly positive end and the other is slightly negative. To form a dipole the molecule must have polar covalent bonds and it must be asymmetrical

Question 23

what are non-polar molecules?

Answer 23

they do not have charged ends.
either the bond is pure covalent or the molecule has polar covalent bonds but the ends are not charged because of its symmetry.

Question 24

what is bond energy?

Answer 24

the amount of energy needed to break the bond

Question 25

what is the bond length?

Answer 25

the distance between the nuclei of 2 covalently bonded atoms.

Question 26

draw and explain making a molecule(page 144)

Answer 26

1. the atoms are far apart,there is no interaction between them and the potential energy is nearly 0
2. As the atoms approach the potential energy decreases because the nucleus from one atom attracts the electron cloud of the other atom.
3. The lowest energy value means this is the most stable position and the atoms bond by sharing electrons.
4. The atoms approach too closely . There is repulsion between the nuclei; the potential energy rises so this is not a stable position and the atoms return to position 3