CHEMISTRY: BONDING

Question 1

Octet rule
1/2

Answer 1

-an atom becomes more stable as its electron configuration becomes like that of a noble gas
-this means two valence electrons for small atoms and eight valence electrons for all others
-the octet rule states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, giving them the same electron configuration as a noble gas
-atoms can achieve the stable configuration by gaining, losing, or sharing electrons

Question 2

Octet rule
2/2

Answer 2

-when an atom loses electrons, it becomes a positive ion
-when an atom gains electrons, it becomes a negative ion
-positive and negative ions attract each other, forming an ionic bond
-we can represent the valence shell of atoms using Lewis electron dot diagrams

Question 3

Lewis electron dot diagrams

Answer 3

-in the figure, sodium (Na) loses an electron to form a sodium ion (Na+), and chlorine gains an electron from sodium to form a chloride ion (Cl-)
-sodium and chloride ions attract each other, forming a sodium chloride crystal
-ionic compounds have high melting and boiling points, but dissolve in polar solvents such as water (water is a polar solvent)
-some atoms form molecules by sharing pairs of electrons, forming what is known as a covalent bond
-in figure 23, two chlorine atoms share electrons
-when two atoms share electrons equally, as in Cl2, we say the bond is a non-polar covalent bond
-however, if two different atoms form a polar covalent bond, they share electrons unequally, the electrons being held closer to one atom than to the other
-ex.HCl—the shared electrons are held closer to chlorine than to hydrogen
-this makes the chlorine end of the molecule slightly negative and the hydrogen end of the molecule slightly positive, hence a dipole

Question 4

Covalent bonds

Answer 4

-compounds can have single, double, or triple covalent bonds

Question 5

[covalent bonds]
Dipole

Answer 5

-two poles
-a molecule that has polar covalent bonds and the distribution of charges is unequal, so that the molecule has a positive and a negative end
-dipoles attract each other, other dipoles, and ions, and they have higher melting and boiling points than nonpolar molecules
-a special type of dipole attraction is the hydrogen bond
-polar solvents are solvents that are dipoles
-ex. water is a dipole and so it has many special properties, such as surface tension and capillary action