Name:____________________________ Block:_________

Electrostatic Forces

An electrostatic force is a forces existing as a result of the between 2 particles.

All is based on the experimentally-derived relationships of electrostatics:

·

· Like charges repel (+ + or - -)

· The between two charged particles, the the attractive force

· The greater the on two particles, the of attraction (or repulsion) between them

Electron Shells REVISITED!

The periodic table shows that patterns in the properties of elements are linked to .

What links atomic number and the properties of elements?

As increases by one, the number of also increases by one.

This means that the elements in the periodic table are also arranged in order of the number of electrons.

What is periodicity?

The Russian chemist Dmitry Mendeleev observed that when the elements are arranged in order of atomic mass, there are

The modern periodic table can be used to analyse trends in properties such as across periods and down groups. (draw this on your diagram above)

What is atomic radius?

The atomic radius of an element is difficult to precisely define because of the uncertainty over the . Several definitions are used.

One definition is half the shortest distance found in the structure of the element.

For non-metallic elements, the is often used as the atomic radius. This is half the internuclear distance between two identical atoms in a single .

For adjacent atoms (e.g. in a covalent crystal of a non-metallic element), the is used as a value for atomic radius. This is half the shortest internuclear distance between two similar non-bonded atoms.

For metallic elements, the is often used as the atomic radius. This is half the shortest internuclear distance between two adjacent atoms in a metallic bond.

Assignment #1A - Lab Activity: Atomic Radius Trends

1. On graph paper, construct a grid using the data listed in table 1.

2. Plot the atomic number (x-axis) of each element against the atomic radius (y-axis) of the same element.

3. Label each point on your graph with the atomic symbol for the element.

4. Can you observe a periodic trend? If so, describe the trend shown by your graph.

Trends in atomic radius in period 3

The atomic radius of the elements across period 3.

This might seem counter-intuitive, because as the numbers of , the radius might be expected to also increase.

However, more than 99% of the atom is empty space – the nucleus and electrons themselves occupy a tiny volume of the atom.

WHY? Increase in proton number

The in the nucleus of the atoms increases across period 3.

This increase in the number of protons increases the of the atoms. The nucleus has attraction for the electrons, pulling them in and so the atomic radiusacross the period.

What is shielding? (follow with the animation and complete notes here. Use the diagrams to help explain shielding)

Explaining atomic radius in period 3

Proton number across period 3, but shielding remains approximately constant.

This causes an increase in , leading to a attraction between the nucleus and the outermost electrons.

This pulls these electrons to the nucleus and results in a radius.

How are electrons arranged?

Electrons are arranged in around an atom’s nucleus.

(also called -principle quantum number n1).

Each shell has a maximum number of that it can hold.

Electrons will fill the shells the nucleus first.

Electrons within each PERIOD

The first shell can only hold a maximum of electrons,

so only includes the elements hydrogen and helium.

What is special about the outer shell of helium?

Elements in all have a first shell.

What happens to electrons in the second shell in period 2?

What is special about the outer shell of neon?

Elements in period 3 have complete first and second shells.

What happens to electrons in the third shell in period 3?

What is special about the outer shell of argon?

Electron trends in the periodic table

Trends down a group:

·

·

Trends across a period:

·

·

Valence Electrons Revisited

Draw the valence electrons on the following atoms: (hint…they all need another energy level)

Valence electrons are:

·

·

Valence electrons are considered electrons

ASSIGNMENT #1B: answer the Hebden questions on a separate page.

Hebden pg. 165 #40-41pg.167 #45-47

4. Arrange the following atoms in order of decreasing atomic radius:

NaAlPClMg

5. Which is the largest atom in Group IV?

6. Which is the smallest atom in Groups VII?

7. Which is the smallest atom in period 5?

8. For each of the following pairs, which of the two species is larger?

Chemistry 11

Unit 9 Chemical Bonding #1

a.

b. N-3 or F-

c. Mg+2 or Ca+2

d. Fe+2 or Fe+3

9.

10. For each of the following pairs, which of the two species is smaller?

a.

b. K+ or Li+

c. Au+ or Au+3

d. P-3 or N-3

11.

12. Order the following groups from largest to smallest radii

a.

b. Ar, Cl-, K+, S-2

c. C, Al, F, Si

d. Na, Mg, Ar, P

e. I-, Ba+2, Cs+, Xe

13.

14. Which species of each pair has the larger radius?

a.

b. Mg or Mg+2

c. K+ or Cl-

d. O or O-2

e. P-3 or S-2

15.

16. What are valence electrons used for by an element?

17. Which elements listed above want to lose electrons?

18. Which elements above want to gain electrons?

19. Determine the element’s number of valence electrons (# of electrons in the “outermost” shell).

Example: Carbon has 4 valence electrons, carbon__4__

a.

b. fluorine _____

c. lithium _____

d. phosphorus _____

e. zinc _____

f. calcium _____

g. carbon _____

h. nitrogen _____

i. iodine _____