S

Elements are the building blocks of

matter. Chapter 2

In this chapter we will be covering…

S The Periodic Table and Chemical Properties!!!

S The Periodic Table and Atomic Theory!

S ELEMENTS!!!

What is an Element? An element is a pure substance that cannot be broken down

or separated into simpler substances.

Each element is made up of only one kind of atom.

There are just over 100 different kinds of elements.

Elements are the same everywhere.

Iron (Fe) atoms found on Earth are identical to iron atoms found on

meteorites, and on Mars.

Chemical Symbols Different countries around the world have different national languages in which the

elements have different names

To make for clearer communication, an international set of chemical symbols are used.

Chemical symbols have either 1 or 2 letters, the first is always capitalized.

In many cases, the symbols are derived from ancient Greek names:

Name Chemical Symbol Greek Name Origin of Elements Symbol

Oxygen O Oxys Genes (acid forming)

Hydrogen H Hydros Genes (water forming)

Chlorine Cl Chloros (pale green)

Potassium K Kalium (latin for potash)

Magnesium Mg Magnesia alba (a place in Greece)

Iron Fe Ferrum (latin for iron)

S

Chapter 2.2 Periodic Table and Chemical Properties

Introducing the Periodic Table of Elements! Chemical Symbols are used to represent elements in the periodic table.

These are arranged by their chemical and physical properties. p. 54

Vocabulary Words

Atomic Mass - mass of average atom (why decimals?)

Atomic Number - number of protons (atoms, by definition, are neutral-no charge; therefore, atomic number is also equal to the number of electrons)

** Atomic number defines the element**

Ionic Charge - electric charge that forms when an atom gains or loses electrons

When an atom gains a charge it is then called an ion

Reading the elements on the PT

Periodic Table is all about the patterns

S one such pattern is that the periodic table is arranged in rows of increasing order of atomic number (that is, number of protons)

Patterns continued...

S a second set of patterns separate the elements into:

1. Metals

2. Non-metals

3. Metalloids

Metals Metals: elements that are typically hard, shiny, malleable, ductile,

and good conductors of heat and electricity.

Mn

Non-Metals Non-Metals: elements that are typically not shiny, malleable, or

ductile and are poor conductors of heat and electricity.

Usually gases or brittle solids at room temperature.

Br I P

Metalloid Metalloids: elements that share some properties with metals and

some properties with non-metals

Ge Si

Comparison Chart

Patterns continued...

SAnother pattern..... SHorizontal rows SCalled periods

The Periodic Table...PERIOD. IN

CR

EA

SIN

G R

EA

CT

IVIT

Y

1

2

3

4

5

6

7

Period number

Last pattern

SLast pattern.....the vertical columns SCalled families SThere are 4 of them

Group 1: The Alkali Metals Location: far left column, group 1

Appearance: shiny, silvery, soft metals

Products: forms water soluble compounds

Reactivity: highly reactive with oxygen and water

Reactivity Trend: Reactivity increases going down the group

Ion Charge: 1+

Li

Na

K

Rb

Cs

Fr

1st family

Group 2:The Alkaline Earth Metals

Location: second column over from left, group 2

Appearance: shiny, silvery metals

Products: forms water insoluble compounds

Reactivity: less reactive than group 1, will burn in air if heated

Ion Charge: 2+

Be

Mg

Ca

Sr

Ba

Ra

2nd family

Group 17: Halogens Location: second column from right, group 17

Appearance: F and Cl are gases, Br is a liquid, I is a solid

Reactivity: highly reactive, react readily with alkali metals

Reactivity Trend: decreases in reactivity going down group

Ion Charge: 1-

F

Cl

Br

I

At

3rd family

Group 18: Noble Gases

Location: Far right column, group 18

Appearance: colourless, odorless gases

Reactivity: most stable and unreactive elements in the periodic table

Products: Do not form compounds easily (full outer shell of electrons)

Atom Charge: 0

He

Ne

Ar

Kr

Xe

Rn

4th family

S

2.3 The Periodic Table and Atomic Theory

Ion charge

The electric charge of an atom when it gains or loses electrons

Atomic Number

The number of protons

(same as the number of electrons in a neutral atom)

Average Atomic Mass

The average of the masses of the atoms in an element

Calculating protons, neutrons and electrons…a review.

isotopes

Add to your notes:

S Atomic number = number of protons (ALWAYS!!!!!!!!) S Where is “all” the mass contains within an atom?

S What two subatomic particles exists there?

S Therefore,

Atomic mass = number of protons + number of neutrons

ISOTOPE: each of two or more forms of the SAME element thatcontain equal numbers of protons but DIFFERENTnumbers of NEUTRONS

Remember the Bohr Model?

S The Bohr model of the atom states that:

1. Electrons surround the nucleus

2. Electrons can have only certain energies

energiesenergies.

Bohr Model

S In the Bohr model electrons are restricted to “shells”.

Each shell can hold a limited number of electrons.

2 8 8 18 18

32

Bohr Model

S In a Bohr model of an atom, the electron shells are filled from the nucleus out with electrons

S One shell is completely filled before any electrons are placed in the next shell.

•A Bohr diagram is a model of the atom that shows the arrangement of electrons in each shell, (energy level), surrounding the nucleus

•There is a maximum of two electrons in the first shell, eight electrons in the second shell, and eight electrons in the third shell.

•Electrons in the outermost shell are called valence electrons.

What is a Bohr diagram?

Steps for drawing Bohr Diagrams

1. Determine the number of protons, neutrons and electrons.

2. Draw a nucleus, write the number of protons and neutrons inside of it.

3. Fill each energy level with electrons until you have no electrons left! 1st

2nd 3rd

4th

Electron shells!

Let’s do these ones together…

He Li C Cl

Write the answers in your NoBo

1. Which elements have outer shells that are full of electrons? Where are

they located on the periodic table?

2. Which elements have only 1 electron in their outer shell? Where are they located on the periodic table?

3. What do you notice about the number of valence electrons (electrons in

the outermost shell) for elements belonging to the same family (vertical column)?

4. Is there a link between the group number (ie. 1 - 18) and the number

of valence electrons an atom has? How are they related?

5. What do you notice about the location of valence electrons for elements belonging to the same period (horizontal row)?

6. Is there a link between the period number and the number of shells an

atom has? How are they related?

Patterns in the Periodic Table

1. Which elements have outer shells that are full of electrons? Where are

they located on the periodic table?

The Noble Gases have outer shells that are full of electrons, and are located in group 18.

Patterns in the Periodic Table

2. Which elements have only 1 electron in their outer shell? Where are

they located on the periodic table?

The Alkali Metals have only 1 electron in their outer shell, and are located in group 1.

Patterns in the Periodic Table

3. What do you notice about the number of valence electrons (electrons in

the outermost shell) for elements belonging to the same family (vertical column)?

Most elements in the same family (or group) have the same number of valence electrons

Patterns in the Periodic Table

4. Is there a link between the group number (ie. 1 - 18) and the number

of valence electrons an atom has? How are they related?

The group number number is indicative of the number of valence electrons a family will have (for elements 1-20). Look at the last digit in the group number to tell you the # of valence electrons. Group number 1 (alkali metals) – all elements in this family have 1 valence electron. Group number 14 – only look at last digit – 4 valence electrons. Group number 18, which has 8 valence electrons Exception to this rule is Helium- it has a full outer shell, but only 2 electrons.

Patterns in the Periodic Table

5. What do you notice about the location of valence electrons for elements

belonging to the same period (horizontal row)?

Elements in the same period have valence electrons in the same shell.

Patterns in the Periodic Table

6. Is there a link between the period number and the number of shells an

atom has? How are they related?

The period number indicates the number of shells that have electrons

Patterns in the Periodic Table

• The period number equals the number of shells in the atom.

1 shell

2 shells

3 shells

4 shells

Patterns of Electron Arrangement in Periods

Except for the transition elements (Groups 3–12), the last digit of the group number equals the number of electrons in the valence shell. Examples: Group 1 = 1 valence electron Group 13 = 3 valence electrons Group 14 = Group 15 = Group 16 = Group 17 =

By losing or gaining electrons, atoms can have the same number of valence electrons as the nearest noble gas. • The noble gas elements have full electron shells and are very stable. They have a stable octet.

4 valence electrons

5 valence electrons

6 valence electrons

7 valence electrons

Patterns of Electron Arrangement in Groups

What are Ions?

•Atoms gain and lose electrons to form bonds.

• The atoms become electrically charged particles called ions.

• Atoms gain and lose electrons in an attempt to have the same number of valence electrons (electrons farthest from the nucleus) as the nearest noble gas in the periodic table.

Ion Formation

What are Cations ? Metals lose electrons and become positive

ions (cations).

Electrically NEUTRAL

Why?

BOHR MODEL

Charges not balanced

= ION

What are Anions ? – NON-Metals GAIN electrons

– and become negative ions (anions).

Electrically NEUTRAL

Why? Charges not balanced

= ION

More Practice

S Checking Concepts (text), p 71 S #5, 8, & 13-16

Homework Check

S Homework: p 71 #5, 8, 13 -16

S 5. (a) Lose (b) Positive S 8. The valence shell is the outermost occupied shell in an atom, while a valence electron is

anelectron that occupies this shell.

S 13. a) Ne – 10p electron arrangement = 2e- 8e- b) S – 16 p, e- arrangement = 2e-, 8e-, 6e- c) K – 19 p, e- arrangement = 2e-, 8e-, 8e-, 1e- d) Be – 4 p, e- arrangement = 2e-, 2e- 14. a) Neon (Ne) b) Nitrogen (N) c) Magnesium (Mg)

S 15. (a) Ar 18p 2, 8, 8 (b) P 15p → → → 2, 8, 5 P3– 15p → → → 2, 8, 8 (c) S 16p → → → 2, 8, 6 S2– 16p → → → 2, 8, 8 (d) Cl 17p → → → →2, 8, 7 Cl– 17p → → → 2, 8, 8 (e) K 19p → → → 2, 8, 8, 1 K+ 19p → → → 2, 8, 8 (f) Ca 20p → → → 2, 8, 8, 2 Ca2+ 20p → → → 2, 8, 8

S 16. The arrangements of the electrons in all ions in question 15 are identical (2, 8, 8) – all full valence

shells

p. 72 chapter review Checking Concepts 1. An element is a pure substance made of only one kind of atom. Specifically, all the atoms of the element have the same number of protons. 6. Shiny, silver coloured, malleable, ductile, conduct

electricity, conduct heat 7. (a) Carbon, other metals (b) Steel

10. Atomic mass measures the mass of an atom of

the element.

11. Number of protons = atomic number

12. A chemical family is a group of elements that

have similar chemical and physical properties.

They occur in columns of the periodic table.

13. Alkali metals, alkaline earth metals, halogens,

noble gases

14. Less reactive

15. They are unreactive.

16. A Bohr model represents the arrangement of

electrons in an atom.

17. (a) The valence shell is the outermost occupied electron

shell in an atom.

(b) A valence electron is an electron that occupies the valence shell. 18. (a) 1 (b) 3 (c) 6 (d) 8 19. (a) Noble gases (b) Their filled valence shells make the atoms of the

noble gases unreactive. 20. Chemistry is the study of matter and its changes. 21. Atomic numbers increase from left to right and from

top to bottom through the periodic table. 22. (a) 51 (b) 33 (c) 13 (d) 34

23. Hydrogen (1.0 amu) ; Oxygen (16.0 amu); Nitrogen (14.0 amu); Rhenium (186.2 amu)

(a) Rhenium (b) Hydrogen 24. (a) Germanium, neodymium(d) Nickel, germanium (b) Neptunium (e) Nickel (c) Germanium 25. (a) Americium (b) Iron, ruthenium (c) Uranium 26. H has the same number of valence electrons as Li, Na, and K. 27. Be 4p 2, 2 Mg 12p 2, 8, 2 Ca 20p 2, 8, 8, 2 28. (a) Aluminum (c) Fluorine (b) Silicon (d) Neon