Isotopes and IonsVARIATIONS ON THE ATOM

Ions!ITS ABOUT PROTONS AND ELECTRONS

Ions Ions are when an atom has an unequal number of p+ and e-

Remember – a stable atom has a neutral overall charge due its equal number of p+ and e-

When an atom loses or gains an e-, its charge changes accordingly◦ Loss of e- means a + charge; gaining an e- means

a – charge for the atom

Losing or Gaining e- . . . . .

If an atom loses an e-, then it has more p+ than e- and it will have an overall positive charge

Different elements’ atoms can lose 1, 2, 3, or even 4 electrons depending on various factors

If an atom has LOST e-, then it is called a CATION or a positive ion◦ A Cation would be written as Al+ (the one being understood) or Al+3

Atoms can also gain electrons If an atom gains electrons (from 1 up to 4), then it will have more e- than p+ and will end up having an overall negative charge

A negatively charged ion is called an ANION

◦ The element is shown this like: Na- (the 1 is understood) or Na-2

The losing or gaining of electrons determines what type of bonds the atoms will form, and which atoms will bond to others

Ions in Water Solution

Using the Periodic Table

Elements in the Main Groups (A), form fairly consistent ions – LEARN TO USE THE CHART

Group IA will form +1 ions; Group 2A form up to +2; Group 3A form up to +3 ions

Group 4A will form either up to -4 or +4 ions Group 5A will form up to -3 ions; Group 6A up to -2; Group 7A form -1; and Group 8A will not form ions at all

Those elements in the B groups vary and we’ll learn those later

IsotopesITS ABOUT PROTONS AND NEUTRONS

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Isotopes

•are atoms of the same element that have different mass numbers.

•have the same number of protons, but different numbers of neutrons.

Isotopes

Atomic SymbolAn atomic symbol

•represents a particular atom of an element.

•gives the mass number in the upper left corner and the atomic number in the lower left corner.

Example: An atom of sodium with atomic number 11 and a mass number 23 has the following atomic symbol:

mass number 23 Na

atomic number 11

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Information from Atomic Symbols

The atomic symbol for a specific atom of an element

gives the

• number of protons (p+),

• number of neutrons (n),

• and number of electrons (e-).

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Information from Atomic Symbols

Examples of number of subatomic particles for atoms

Atomic symbol

16 31 65

O P Zn 8 15 30

8 p+ 15 p+ 30 p+

8 n 16 n 35 n 8 e- 15 e- 30 e-

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Learning Check

Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following:

12C 13C 14C 6 6 6

protons ______ ______ ______

neutrons ______ ______ ______

electrons ______ ______ ______

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16

12C 13C 14C 6 6 6

protons 6 p+ 6 p+ 6 p+

neutrons 6 n 7 n 8 n

electrons 6 e- 6 e- 6 e-

Solution

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Write the atomic symbols for atoms with the following subatomic particles:

A. 8 p+, 8 n, 8 e- ___________

B. 17p+, 20n, 17e- ___________

C. 47p+, 60 n, 47 e- ___________

Learning Check

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A. 8 p+, 8 n, 8 e- 16O

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B. 17p+, 20 n, 17e- 37Cl 17

C. 47p+, 60 n, 47 e- 107Ag 47

Solution

Learning Check1. Which of the pairs are isotopes of the same element?2. In which of the pairs do both atoms have 8 neutrons?

A. 15X 15X 8 7

B. 12X 14X 6 6

C. 15X 16X 7 8

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SolutionB. 12X 14X

6 6

The atomic symbols in “B.” represent isotopes of carbon with 6 protons each, but one has 6 neutrons and the other has 8.

C. 15X 16X

7 8

These isotopes of nitrogen and oxygen have 8 neutrons.

Isotopes of Magnesium

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Isotopes of Magnesium

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Isotopes of Sulfur

A sample of naturallyoccurring sulfur containsseveral isotopes with thefollowing abundances

Isotope % abundance 32S 95.02 33S 0.75 34S 4.21 36S 0.02

32S, 33S, 34S, 36S16 16 16 16

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Ions and Isotopes in Review

Stable atom: #p+ = #n0 = #e-

Atomic Mass - #n0 = # p+

Atomic Mass - #p+ = #n0

If charge is 0, then #p+ = #e-

If charge is positive, then #p+ > #e- Cation

If charge is negative, then #p+ < #e- Anion

Examples: Li-1 has gained an electron, meaning there is one more negative charge than positive ones

◦ It has 3 p+ and 4 e-

Li+1 has lost an electron, meaning there is one more positive charge than negative ones

◦ It has 3 p+ and 2 e-

◦ REMEMBER: The # of p+ DO NOT CHANGE◦ Only the number of n0 (isotope) and e- (ion) change

Cf-3 has an atomic number of 98◦ This means it has 98 p+

◦ Its atomic mass is 216◦ It has 118 n0, (216 – 98), making it an ion and an isotope!◦ Since it has a -3 charge, the number of e- will be 101; (98 + 3)

◦ Zn+1 has 30 p+ and n0; but due to the +1 charge, it has only 29 e-