FORMING BONDS
Sometimes atoms react together by transferring electrons to form
chemical bonds. This happens when metals react with non-metals. If the
reacting atoms are all non-metals, then the atoms share electrons to form
chemical bonds. In other words, chemical bonds either occur as the result of the
atoms sharing the electrons between them, or by one atom donating electrons to
another. The number of the electrons present in the atom’s outer shell
determines the number of bonds it will form. The outer shell (or else called
valence shell) of an atom can contain a maximum of 8 electrons, depending on its
position in the periodic table. All atoms ‘want’ to have a full outer shell of
electrons.
Forming ions
When a metal bonds with a non-metal, the metal atom gives one or more
electrons to the non-metal atom. Both atoms become charged particles called
ions
* metal atoms form positively charged ions (+)
*non-metal atoms from negatively charged ions (-)
Opposite charges attract each other. There are strong attractions between the
positive and the negative ions in a compound of a metal and a non-metal. These
strong forces of attraction are the chemical bonds that form. They are called
ionic bonds.
Forming molecules
Non-metal atoms bond to each other in a different way. The outermost shells of
their atoms overlap and they share electrons. Each pair of shared electrons
forms a chemical bond between the atoms. These are called covalent bonds. No
ions are formed. Such bonds lead to stable molecules if they share electrons in
such a way as to create a noble gas configuration for each atom.
1. Complete the text that follows with words from the box
covalent
lose
gain
ionic negative
attract
share
positive
Metal atoms form _____________________ ions because they __________ one or
more electrons when they combine with non-metals. Non-metal
atoms______________ electrons in the reactions, forming _________________ ions. The
oppositely charged ions _________________ each other. This is called _____________
bonding. When non-metals combine with each other, they form _________ bonds.
Their atoms _________ electrons.
2. Answer the following questions
a. Why do some atoms share electrons? Which atoms are they?
b. Why do some atoms transfer electrons? Which atoms are they?
c. What is the MAIN difference between an ionic and a covalent bond?
3. Indicate whether each statement is true (T) or false (F).
a.
b.
c.
d.
e.
f.
Covalent bonding involves sharing electrons.
Atoms react to gain full outer shell of electrons.
Covalent bonding creates ions with the electronic structure of a noble gas.
In covalent bonding, atoms lose or gain electrons.
In ionic bonding atoms share electrons.
Ions with opposite charges attract each other
4. Circle the word(s) that best describe the meaning of the words in bold
a. form ( create – destroy – gain)
b. donate ( gain – give – take)
c. contain ( miss – have – give)
d. bond(v) (react – tie – loosen)
e. outer shell of the atom ( valence shell – electron shell –inner shell)
5. What do the words in bold refer to?
This (line 2)
a. transferring of electrons b. sharing of electrons
Another
(line 6)
a. electron
b. bond
c. atom
It
(line 7)
a. bond
b. electron
c. atom
Its
(line 8)
a. shell’s
b. electron’s
c. atom’s
they (line 17)
a. bonds
b. forms
c. ions
c. atoms