The Periodic TableThe Periodic Table

Dmitri Mendeleev (1834 - 1907)Dmitri Mendeleev (1834 - 1907)

Elements are arranged:

Vertically into Groups

Horizontally Into Periods

Why?

If you looked at one atom of every element in a group you would

see…

Each atom has the same number of electrons in its outermost shell.

• An example…

The group 2 atoms all have 2 electrons in their outer shells

Be (Beryllium)

Atom

Mg (Magnesium) Atom

• The number of outer or “valence” electrons in an atom affects the way an atom bonds.

• The way an atom bonds determines many properties of the element.

• This is why elements within a group usually have similar properties.

If you looked at an atom from each element in a period

you would see…

Each atom has the same number of electron shells.

An example…

The period 4 atoms each have 4 electron containing shells

K (Potassium)

AtomFe (Iron) Atom

Kr (Krypton)

Atom

4th Shell

Each group has distinct properties

• The periodic Table is divided into several groups based on the properties of different atoms.

Alkali Metals

Soft, silvery coloured metals

Very reactive!!!

Group 1A: Alkali MetalsGroup 1A: Alkali Metals

Cutting sodium metalCutting sodium metal

Reaction of potassium + H2O

Alkali Metals reacting with water:

• Li (Lithium) – least reactive

• Na (Sodium)• K (Potassium)• Rb (Rubidium)• Cs (Cesium) – more reactive

What would you expect from Francium?!?!

MagnesiumMagnesium

Magnesium Magnesium oxideoxide

Group 2A: Alkaline Earth MetalsGroup 2A: Alkaline Earth Metals

Alkaline Earth Metals

Silvery-White Metals

Fairly reactive

Many are found in rocks in the earth’s crust

Transition Metals

Malleable (easily bent/hammered into wires or sheets)

Most are good conductors of electricity

How many things can you think of that have Transition Metals in

them?

Metalloids lie on either side of the “staircase”

They share properties with both metals and non-metals

Si (Silicon) and Ge (Germanium) are very important “semi-conductors”

What are semiconductors used in?

Nonmetals

Brittle

Do not conduct electricity

Most are poisonous

Fairly reactive – react with alkali metals (eg) Na+ and Cl-

Halogens

Chlorine Gas was used as a chemical weapon during World War I.

It was used by the Germans in World War II.

Chlorine Gas• The Germans were the first to use Chlorine gas

at Ypres in 1915• Chlorine gas is a lung irritant• The symptoms of gas poisoning are bright red

lips, and a blue face• People affected die a slow death by suffocation• Decades later men who thought they had

survived the war died from lung diseases such as Emphysema

CHLORINE

Unreactive

Gases at room temperature

Noble Gases

Jellyfish lamps made with noble gases artist- Eric Ehlenberger

Colors Noble Gases produce in lamp tubes:

• Ne (Neon): orange-red

• Hg (Mercury): light blue

• Ar (Argon): pale lavender

• He (Helium): pale peach

• Kr (Krypton): pale silver

• Xe (Xenon): pale, deep blue

Lanthanide SeriesActinide Series

• (A) Periods of the periodic table, and (B) groups of the periodic table.

• Chemical “Groups”– IA are called alkali metals because they react with

water to form an alkaline solution (basic)• They are very reactive– Group IIA are called the alkaline earth metals

because they are reactive, but not as reactive as Group IA.

• They are also soft metals – Group VIIA are the halogens

• These need only one electron to fill their outer shell• They are very reactive

– Group VIIIA are the noble gases as they have completely filled outer shells

• They are almost non-reactive.

• Four chemical families of the periodic table: the alkali metals (IA), the alkaline earth metals (IIA), halogens (VII), and the noble gases (VIIIA).

Metal: Elements that are usually solids at room temperature. Most elements are metals.

Non-Metal: Elements in the upper right corner of the periodic Table. Their chemical and physical properties are different from metals.

Metalloid: Elements that lie on a diagonal line between the metals and non-metals. Their chemical and physical properties are intermediate between the two.

An atom consists of aAn atom consists of a • nucleusnucleus

– (of (of protonsprotons and and neutronsneutrons) ) • electronselectrons in space about the nucleus. in space about the nucleus.

The The AtomAtom

NucleusNucleus

Electron cloudElectron cloud

ATOM ATOM COMPOSITIONCOMPOSITION

•protons and neutrons in protons and neutrons in the nucleus.the nucleus.

•the number of electrons is equal to the number the number of electrons is equal to the number of protons.of protons.

•electrons in space around the nucleus.electrons in space around the nucleus.

•extremely small. One teaspoon of water has 3 extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has times as many atoms as the Atlantic Ocean has teaspoons of water.teaspoons of water.

The atom is mostlyThe atom is mostlyempty spaceempty space

Compounds

– composed of 2 or more elements in a fixed ratio

– properties differ from those of individual elements

– EX: table salt (NaCl)

AA MOLECULEMOLECULE is 2 more atoms is 2 more atoms bonded together – they may be the same bonded together – they may be the same element (ie diatomic molecule) or they may element (ie diatomic molecule) or they may be different elements (ie caffeine)be different elements (ie caffeine)Composition of molecules is given Composition of molecules is given

by aby a MOLECULAR FORMULAMOLECULAR FORMULAHH22OO CC88HH1010NN44OO22 - caffeine - caffeine

ELEMENTS THAT EXIST ASELEMENTS THAT EXIST AS DIATOMICDIATOMIC MOLECULES MOLECULES

Remember:

The “GENS”These elements exist as PAIRS when ALONE.

Hydrogen (H2)

Nitrogen (N2)

Oxygen (O2)

Halogens

(F2, Cl2, Br2, I2)

(P4 and S8)

IsotopesIsotopes• Atoms of the same element (same Z) but

different mass number (A).• Boron-10 (10B) has 5 p and 5 n• Boron-11 (11B) has 5 p and 6 n

10B

11B

Isotopes & Isotopes & Their UsesTheir UsesBone scans with radioactive technetium-99.

CARBON-14 – RADIOACTIVE ISOTOPE

• Occurs in trace amounts in the atmosphere

• Absorbed into living organisms

• The half-life of carbon-14 is approx 5700 years (when half the C-14 is converted to N-14)

Atomic Symbols

Show the name of the element, a hyphen, and

the mass number in hyphen notation

sodium-23

Show the mass number and atomic number in

nuclear symbol formmass number 23 Na

atomic number 11

Isotopes? Which of the following represent

isotopes of the same element? Which element is it?

234 X 234

X235

X238

X

92 93 92 92

1 2 3 4

IONS IONS • IONS are atoms or groups of atoms with a positive or

negative charge.

• Donating an electron from an atom gives a CATION with a positive charge

• Accepting an electron to an atom gives an ANION with a negative charge

• To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O

Forming Cations & AnionsForming Cations & AnionsA CATION forms when an atom loses one or more electrons.

An ANION forms when an atom gains one or more electrons

Mg --> Mg2+ + 2 e- F + e- --> F-

PREDICTING ION CHARGESPREDICTING ION CHARGES

In general

• metals (Mg) lose electrons ---> cations (Mg2+)

• nonmetals (F) gain electrons ---> anions ons (F(F--))

– When an atom or molecule gain or loses an electron it becomes an ion.

• A cation has lost an electron and therefore has a positive charge

• An anion has gained an electron and therefore has a negative charge.

Charges on Common Charges on Common IonsIons

-1-2-3+1

+2

By losing or gaining e-, atom has same By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.number of e-’s as nearest Group 8A atom.

Learning Check – Counting

State the number of protons, neutrons, and electrons in each of these ions.

39 K+ 16O -2 41Ca +2

19 8 20

#p+ ______ ______ _______

#no ______ ______ _______

#e- ______ ______ _______

– Elements with 1, 2, or 3 electrons in their outer shell tend to lose electrons to fill their outer shell and become cations.

• These are the metals which always tend to lose electrons.

– Elements with 5 to 7 electrons in their outer shell tend to gain electrons to fill their outer shell and become anions.

• These are the nonmetals which always tend to gain electrons.

– Semiconductors (metalloids) occur at the dividing line between metals and nonmetals.

What would the charge be on a sodium ion?

EXAMPLE

Since sodium in in Group IA it is a metal and so wouldLOSE an electron

You can tell how many would be lost by the group numberGroup 1A elements lose 1 electron

So the charge would be +1Remember an electron is negatively charged. When you lose them atom becomes positively charged…

when you gain them it becomes negatively charged

How would you right the symbol for the sodium CATION?

EXAMPLE

Na+1

How many outer electrons does sodium have before it loses one?

It has 1…remember the group number!