Catalyst – October (22-2), 2009

Objectives SWBAT determine the trends for atomic size

and electronegativity.

Catalyst What family is Calcium in? What period is Rb in? Who was the first person to leave spaces for

undiscovered elements on the periodic table? How did Mosley’s periodic table differ from all

of the tables that came before his?

Today’s Agenda

Catalyst Finishing Families More secrets of the PT: Atomic

Size and Electronegativity Exit Question

Alkali Metals

Alkali metals are very reactive – even with water!

Sodium + Water EXPLOSION!

Alkaline Earth Metals

Alkaline Earth metals are also very reactive Shiny solids that are harder than Alkali

metals Alkaline Earth Metal Spotlight: CALCIUM

Calcium is essential for human life, especially in maintaining bones and teeth

Found widely in nature combined with oxygen Abrasives in toothpaste and emery boards

Magnesium Demo!

Boron’s Group

Gallium is a silver metal that literally melts in your hand!

Don’t try this

yourself!

Carbon’s Group

Carbon is one of the most important elements on Earth! There is a whole branch of chemistry

dedicated to studying carbon – ORGANIC CHEMISTRY!

If you are a science major in college, you will most likely take Organic

Silicon is the second most abundant element on Earth! Use in computer chips and solar cells Found in quartz, sand, and glass

Nitrogen’s Group

Metals, nonmetals, and metalloids! Nitrogen, which you breathe, can

form some of the most explosive compounds known to man

Arsenic is a toxic substance that was used to treat some illnesses back in the day

Bismuth is used in fire sprinklers

Oxygen’s Group

Oxygen We must breathe oxygen to survive…

so it’s pretty important Reacts with some of the noble gases

Sulfur Hydrogen sulfide smells like rotten egg

Selenium Used in solar panels because it can

convert light into energy

Fluorine (really fluoride) is added to toothpaste

Chlorine gas is a deathly green gas that was first used as a form of chemical WARFARE in WWII

Halogens (Fluorine’s Group)

Noble Gases (Helium’s Group) Noble gases do not react with other

elements very often – they are already “happy” They can be called “inert” because

they don’t react Neon is used in neon lights Helium Voice!

Transition Metals

Conduct electricity Can form different ions (We’ll learn

more about ions later!) Many found in nature – found all

over the world (map on page 200) Uses

Found in alloys, wires, plastics, etc. Your body needs trace (small)

amounts many of them

What is Atomic Size?

Atomic size is… How big an atom is Also known as atomic radius

Graphing Atomic Size (Radii)Draw a line graph

X-axis: Element Y-axis: Atomic Radii (picometers)

Part 1 – points = dotsPart 2 – points = squares

Elements and their Atomic Radii (1)

Element Atomic Radius (picometer)

Hydrogen 37

Lithium 152

Sodium 186

Potassium 227

Rubidium 248

Cesium 265

1 picometer = 1 x 10-12 m

Elements and their Atomic Radii (2)

Element Atomic Radius (picometer)

Lithium 152

Beryllium 112

Boron 85

Carbon 77

Nitrogen 75

Oxygen 73

Fluorine 72

Neon 71

1 picometer = 1 x 10-12 m

What trend(s) do

you notice?

Atomic size DECREASES as you go across the Periodic TableA

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Atomic Size

Key Point #1: Atomic size increases as you go down the periodic table and decreases as you go left to right across the periodic table.

Practice Problems

Rank the following elements in order of increasing atomic size based on location on the periodic table (smallest to biggest)

Fr, Sc, P, Pd

F, As, Tl, S

Magnesium, Hydrogen, Francium, StrontiumFluorine, Sulfur, Arsenic, Thallium

Practice Time!

1. T or F? Atomic size decreases as you move right across the periodic table.

2. T or F? As you move down the Periodic Table, atoms get smaller.

3. Rank the following sets of elements in order of increasing atomic size (small big).

Set A: Bh, Mn, Re, Tc Set B: Sb, I, Ag, Ru Set C: Y, Ti, Sg, Ta

4. Rank the following sets of elements in order of decreasing atomic size (big small).Set A: Cl, At, I, F, Br Set B: Te, Xe, Sn, In

Set C: Rb, K, Sr, Ca

What is electronegativity?

Electronegativity is… The ability of an atom to attract electrons to itself in a chemical bond

How much an atom wants electrons

Graphing Electronegativity

Draw a line graph X-axis: Element Y-axis: Electronegativity

Part 1 – points = dotsPart 2 – points = squares

Elements and their Electronegativity (1)

Element Atomic Radius (Paulings)

Hydrogen 2.20

Lithium 0.98

Sodium 0.93

Potassium 0.82

Rubidium 0.82

Cesium 0.79

Francium 0.70

Elements and their Electronegativity (2)

Element Atomic Radius (Paulings)

Lithium 0.98

Beryllium 1.57

Boron 2.04

Carbon 2.55

Nitrogen 3.04

Oxygen 3.44

Fluorine 3.98

What trend(s) do

you notice?

Electronegativity

Key Point #2: Electronegativity decreases as you go down the periodic table and increases as you go left to right across the periodic table.

Practice Problems

Rank the following elements in order of increasing electronegativity based on location on the periodic table (smallest to biggest)

Mg, Sr, Be, Ra

Cl, Si, Al, S, P

Radon, Strontium, Magnesium, BerylliumAluminum, Silicon, Phosphorus, Sulfur, Chlorine

Practice Time!1. T or F? Electronegativity decreases as you

move left across the periodic table.2. T or F? As you move down the Periodic

Table, atoms get more electronegative.3. Rank the following sets of elements in order

of increasing electronegativity (small big). Set A: Bh, Mn, Re, Tc Set B: Sb, I, Ag, Ru Set C: Y, Ti, Sg, Ta

4. Rank the following sets of elements in order of decreasing electronegativity (big small).Set A: Cl, At, I, F, Br Set B: Te, Xe, Sn, In

Set C: Rb, K, Sr, Ca

How does atomic size related to electronegativity?

Key Point #3: Atomic size is indirectly related to electronegativity

ELECTRONEGATIVITY

ATOMIC SIZE

As electronegativity increases, atomic size decreases!

Why is this relationship true? Atoms with HIGH

ELECTRONEGATIVITIES hold their electrons very close!

Sooooo, the atomic size decreasesHigh or low electronegativity?

Large or small atomic size?

Group Work Time!

Exit Question

1. Which element has atoms with the smallest size: Cl, Se, P, or F?

2. Which element has the largest electronegativity: Ag, Cu, Hg, or Zn?

3. What is the relationship between atomic size and electronegativity?