The Why and How of Ions Featuring the Return of Bohr-Rutherford Diagrams and the Periodic Table.

The Why and How of Ions

Featuring the Return of Bohr-Rutherford Diagrams and the Periodic Table

Bohr-Rutherford Diagrams

Bohr-Rutherford diagrams (or simply Bohr diagrams) are used to show the arrangement of electrons in the atom, e.g.:

How To Draw Bohr Diagrams

1) Find your element on the periodic table.

2) Determine the number of electrons, which for a neutral atom is equal to the number of ?



2) Determine the number of electrons, which for a neutral atom is equal to the number of protons, which is equal to the ?



2) Determine the number of electrons, which for a neutral atom is equal to the number of protons, which is equal to the atomic number.


3)Determine which period (row) your element is in.

Elements in the 1st period have one energy level or shell.

Elements in the 2nd period have two, and so on.


CC

4) Draw a nucleus with the element symbol (and optionally, the #s of protons and neutrons) inside.

5) Draw the shells around the nucleus.

Carbon is in the 2nd period, so it has two energy levels or shells.


6) Add the electrons.

Carbon has 6 electrons.

The first shell can only hold ?

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6) Add the electrons.

Carbon has 6 electrons.

The first shell can only hold 2 electrons.

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You need to add 4 more so these go in the 2nd shell.

The 2nd shell can hold up to ?CC


You need to add 4 more so these go in the 2nd shell.

The 2nd shell can hold up to 8 electrons; the 3rd shell can hold 18, but the elements in the first few periods only use 8 electrons.

CC


7) Check your work: Count your electrons per shell and your total electrons!

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Bohr Diagrams: Practice

Try drawing Bohr diagram for each of the following elements on your own:

a) H

b) He

c) O

d) Al

e) Ne

f) K

CC



a) H – 1 electron

b) He

c) O

d) Al

e) Ne

f) K

HH



a) H

b) He - 2 electrons

c) O

d) Al

e) Ne

f) K

HeHe



a) H

b) He

c) O - 8 electrons

d) Al

e) Ne

f) K

OO



a) H

b) He

c) O

d) Al - 13 electrons

e) Ne

f) K

AlAl



a) H

b) He

c) O

d) Al

e) Ne - 10 electrons

f) K

NeNe



a) H

b) He

c) O

d) Al

e) Ne

f) K - 19 electrons

KK

Lewis Dot Diagrams

The electrons in the outermost shell are called ?

Lewis Dot Diagrams

The electrons in the outermost shell are called valence electrons.

Lewis Dot Diagrams

The electrons in the outermost shell are called valence electrons.

Lewis Dot Diagrams are abbreviated Bohr Diagrams that show just these outermost electrons, e.g.:

Valence Electrons and Families

Note that both hydrogen (H) and potassium (K) have just ? electron in their outermost shell.

Note also that these elements are both found in the ? column of the periodic table.

This is not a coincidence!

Valence Electrons and Families

Note that both hydrogen (H) and potassium (K) have just 1 electron in their outermost shell.

Note also that these elements are both found in the ? column of the periodic table.


Valence Electrons and Groups

Note that both hydrogen (H) and potassium (K) have just 1 electron in their outermost shell.

Note also that these elements are both found in the 1st column of the periodic table.



All elements in the same group (column) have the same number of electrons in their outermost shell (ref. p. 150).

It is these electrons that determine the behavior of the element, including how it reacts with other elements – and how it forms ions.


Let’s look at these groups or families in more detail. . . .

ALKALI METALS

1 valence electron

(Hydrogen is not officially a member)

• Soft and silvery metals

• Very reactive, esp. with water

ALKALINE EARTH METALS2 valence

electrons

• White and malleable

• Reactive, but less so

TRANSITION METALS

(the Groups in the middle)

BORON FAMILY

3 valence electrons

• Most are metals

• Boron is a metalloid.

CARBON FAMILY 4 valence

electrons

• Contains metals, metalloids, and a non-metal: carbon (C)

NITROGEN FAMILY 5 valence

electrons

• Contains metals, metalloids, and non-metals

OXYGEN FAMILY 6 valence

electrons

• Mostly non-metals

• Reactive

Halogens7 valence

electrons

• All are non-metals

• Very reactive

Noble GasesFull outer shell• Exist as gases• Not reactive with

other elements• Do not form

ions.

The Why of Ions

The Noble Gases do not react and do not form ions because they already have what all atoms want: full outer shells.

The How of Ions

Atoms will either gain electrons to fill their outer shell (as in the case of the non-metal chlorine)

The How of Ions

or lose electrons to go down to their last full shell (as in the case of the metal sodium)

Tune in next time. . . .

More details on the formation of ions will be revealed tomorrow.

For now, answer the questions:

p. 148 #1-5

p. 150 #1-3

p. 153 #10, 11

The Why and How of Ions Featuring the Return of Bohr-Rutherford Diagrams and the Periodic Table.

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