Bonding pt 2 Flashcards
Between MgO and NaCl which one is stronger/has a higher melting point
MgO is stronger/has a higher melting point than NaCl because when the ions are smaller and or have higher charges they have higher melting points and are stronger.
The ions involved in MgO are Mg2+ and O2+ where as in NaCl it is Na+ and Cl-
What effect does going down a group have on ionic radii
It increases because the ions have more shells of electrons
Why are positive ions smaller than negative ions
Positive ions are smaller because it has one less shell of electrons and the ratio of protons to electrons has increased so there is a greater net force on remaining electrons holding them more closely
Define electronegativity
The ability of an atom to attract the pair of electrons in a covalent bond to itself
What effects electronegativity (3)
The number of protons in the nucleus;
The distance from the nucleus;
The amount of screening by inner electrons
Why exactly does the electronegativity increase?
Electronegativiity incrases across a period-Number of protons increases and atomic nucleus decreases because the eletrons in the same shell are pulled in more
It decreases down a group bcause the distance between the nucleaus and the outershell increases and the shielding of inner shell elctrons increases
How do you get a non polar bond
Both bonding elements have the same electronegativities
How do you get a polar bond
Bonding atoms have different electronegatuvities
why is ice less dense than liquid water
Ice is less dense than water because the hydrogen bond orientation in ice causes the molecules to push farther apart, lowering the density.
Why are negative ions bigger than the corresponding atom
It has more electrons than the correspondng atom but the same number of protons so the pull of the nucelus is shared over more electrons and the attraction per electron is less making the ion bigger
Symmetrical molecules
A symmetrical molecule (all bonds identical and NO lone pairs) will not be polar even if individual bonds wothin the molecule are polar
What are the ionic formulas for Sulfate Hydroxide Nitrate Carbonate and Ammonium
SO4^2-
OH-
NO3^-
CO3^-2
NH4^+
Why are symmetrical molecules non polar
The individual dipoles on the bonds cancel out due to symmetrical shape of the molecule
Features of Graphite (5)
-Layers slide over each other as there are weak VDW forces between the layers
-Has delocalised electrons between the layers allowing it to conduct electricity
-Layers are far apart–>Low density
-Lots of strong covalent bonds–>very high melting point
-Graphite is insoluble–>Bonds to strong to break
Each carbon is bonded 3 times with each other so forms hexagonal rings
Features of diamond (3)
-Tightly packed rigid arrangement allows heat to be conducted well
-Very high MP due to many strong covalent bonds-also very hard-
-Doesnt conduct electricity as it has no delocalised electrons
Each carbon is bonded 4 times so forms a tetrahedral shape
