Chemical bonding Flashcards
how are ionic bonds formed?
when electrons are transferred between atoms to make positive or negative ions
how are covelant bonds formed??
when atoms share pair of electrons
what is electronegativity
is the tendency for an atom of a given chemical element to attract shared electrons when forming a chemical bond
state the laws of electronegativity
=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
what is the electronegativity of a pure covalent bond?
0
what is the electronegativity of an ionic bond?
bigger or equal to 2
what is the electronegativity of a polar covalent bond?
0 to 1,9
explain “atoms which make more than 4 bonds”
examples are sulfur and phosphorus, these elements have empty d orbitals to which electrons can move if enough energy is available in a reaction
Multiple bonds??
=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.
Dative covalent bonds??
they are formed by overlapping of a filled orbital containing a lone pair with the empty orbital of another atom or ion.
what is the symbol for dative covalent bonds??
see page 139
Shapes of molecules
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.
VSPER?
predicts that there is repulsion between pairs of electrons
lone pair -lone pair>shared pair-lone pair>shared pair -shared pair
shape of molecule(molecules containing a single bond )
linear
bond angle is 180 degrees
shape of molecule(molecules containing of 2 single bonds )
linear
bond angle is 180 degrees
shape of molecule(molecules containing 3 single bonds )
trigonal planar
bond angle is 120 degrees
shape of molecule(molecules containing 4 single bonds )
tetrahedral
bond angle is 109 degrees
shape of molecule(molecules containing 3 single bonds and a lone pair )
pyramidal
bond angle is 107,5 degrees
shape of molecule(molecules containing 2 single bonds and 2 lone pairs )
angular
bond angle is 105 degrees
shape of molecule(molecules containing 5 single bonds )
trigonal bi-pyramid
bond angle is 120 degrees in the plane and top and bottom bond at 90 degrees to the plane
shape of molecule(molecules containing 6 single bonds )
octahedral
bond angle is 90 degrees
what are polar molecules?
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
what are non-polar molecules?
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.
what is bond energy?
the amount of energy needed to break the bond
what is the bond length?
the distance between the nuclei of 2 covalently bonded atoms.
draw and explain making a molecule(page 144)
- the atoms are far apart,there is no interaction between them and the potential energy is nearly 0
- As the atoms approach the potential energy decreases because the nucleus from one atom attracts the electron cloud of the other atom.
- The lowest energy value means this is the most stable position and the atoms bond by sharing electrons.
- 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
