Properties of Atoms and the Periodic Table

Chapter 17Pages 504-533

Section 1: Structure of the Atom

What is an atom??? First, let’s review what an element is: An element is matter that is composed ONLY

of one type of atom.

An atom is the smallest piece of matter that still retains the properties of the element.

Example: The element oxygen is composed of only oxygen atoms.

Composition of Atoms Atoms are composed

of 3 general particles: Particle Charge Location

Proton Positive (+)

Nucleus

Neutron No charge (neutral)

Nucleus

Electron Negative (-)

Outside the Nucleus

How are atoms of the various elements different??? Atoms of different elements contain

DIFFERENT NUMBERS OF PROTONS!!!

Quarks Quarks are very small particles that make

up both protons and neutrons!

At this time, scientists do not think that electrons can be broken down into smaller pieces.

Finding Quarks To study quarks, charged particles are

accelerated (almost to the speed of light) and forced to collide with a proton. The collision causes the proton to break apart.

The Large Hadron Collider, located in Switzerland and France, consists of a circular tunnel with a circumference of 17 miles!

http://www.wimp.com/largehadron/

Finding Quarks

The Changing Atomic Model 400 BC: Democritus proposed the idea

that atoms make up all substances.

Aristotle said matter was uniform throughout and was not composed of smaller particles.

1800’s: John Dalton proved atoms exist.

The Electron Cloud Model An electron cloud is the area around the

nucleus of an atom where the electrons are most likely to be found.

The electron cloud is 100,000 times larger than the diameter of the nucleus. Electrons are MUCH smaller than protons.

Atomic Model Example Example: We want to build a model of a

hydrogen atom. We will represent the nucleus with a marble that has a radius of 2.4 cm.

Any guesses as to how big we need to make the entire atom???

1.2 kilometers!!!!!!!

Section 2: Masses of Atoms

Atomic Mass Protons and Neutrons have about the

same mass (1.67 x 10-24g)……VERY small

Both protons and neutrons have 1,836 times more mass than an electron.

Atomic Mass Unit (AMU) is the measurement used for the mass of a proton or neutron.

What element is it? You need to know how many protons it

has!

The number of protons in an atom is equal to the atomic number.

Mass Number The mass number of an atom is the sum of

the number of protons AND the number of neutrons in the nucleus.

So how do you find the number of Neutrons???

# Neutrons = mass # - atomic #

Lets Do an Example Element: Strontium, (#38)

Atomic Number: 38 Mass Number: 88 Number Protons: 38 Number Neutrons: 50 Number Electrons: 38

Carbon Dating…What is it??? Carbon dating uses isotopes of carbon that

are radioactive and have a half-life to date once living organisms.

Wrong King of Carbon Dating This is NOT carbon dating.

Isotopes Isotopes are atoms of the same element

with different numbers of NEUTRONS!!!!

Identifying Isotopes To identify each isotope, write the mass

number of the isotope behind the element name: Boron-10 Boron-11

The average atomic mass is the weighted –average mass of the mixtures of it’s isotopes.

Isotope Example Chromium-58

# Protons: _____ # Neutrons: _____ # Electrons: _____

Chromium-63 # Protons: _____ # Neutrons: _____ # Electrons: _____

Section 3: The Periodic Table

Organizing the Elements Late 1800’s Dmitri Mendeleev, Russian chemist Ordered elements by increasing atomic masses. Left blank spaces in the table to keep the

elements lined up.He predicted the properties ofelements not yetdiscovered! (andwas accurate!)

Organizing the Periodic Table The vertical

columns are labeled 1-18 and are called groups.

The horizontal columns are labeled1-7 and are called periods

Elements in each group have similar properties

Electron Cloud Structure Electrons are located outside of the

nucleus of an atom…but do we know exactly where?

Electrons have different amounts of energy, and exist in different energy levels within the atom.

Continued…electron cloud structure The closest electrons to the nucleus have

the lowest amounts of energy, where the farthest electrons away from the nucleus have the most energy.

Elements in the same group have thesame number of electrons in their outer energy level.

Implications of Electron Cloud Structure The number of electrons in the outer

energy level determines the chemical properties of that element.

Electrons in the outerenergy level also calledValence Electrons.

Electron Dot Diagrams Electron dot diagrams use the symbol of

the element and dots to represent the electrons in the outer energy level.

Also can be called Lewis Structures.

Bohr Structures

Bohr Model- includes all electrons.

Elements in the UniverseZ Element Parts per million

1 Hydrogen 739,000

2 Helium 240,000

8 Oxygen 10,400

6 Carbon 4,600

10 Neon 1,340

26 Iron 1,090

7 Nitrogen 960

14 Silicon 650

12 Magnesium 580

16 Sulfur 440

Elements and Their Properties

Chapter 19Pg. 568-599

Section 1: Metals

Properties of Metals 1. Good conductors of heat and electricity 2. All but mercury are solid at room

temperature.

More Properties of Metals 3. Metals reflect light. This property is

called luster

More Properties of Metals 4. Metals are malleable- they can be

hammered or rolled into sheets. 5. Metals are ductile- they can be drawn

into wires.

Ionic Bonding in Metals Metals usually have 1-3 electrons in their

outer energy levels. Metals can “give” one or more of their

outer electrons to another atom, thus bonding them together by sharing electron(s).

Metallic Bonding

Metallic bonding-electrons in outer energy level are shared between all the atoms.

Alkali Metals Group 1 Softer than most metals Most reactive of all the metals especially with air

and water. Do not exist in the earth in their elemental form,

so they are stored in substances that are not reactive, like oil.

Group 1 Alkali metals have 1 electron in their outer shell,And combine easily with group17 elements.

Alkaline Earth Metals Group 2 of the Periodic Table Each atom of this group has 2 valence

electrons.

Alkaline Earth Metals- Uses Fireworks! Magnesium makes a white

explosion, and strontium produce red. Magnesium used in making cars, planes,

and spacecraft. Our bones need calcium to keep them

strong.

Transition Elements Found in groups 3-12 in the Periodic Table Often form colored compounds. Example

gems (chromium), some paints made from compounds of cobalt and/or cadmium.

Iron, Cobalt and Nickel All three elements are used to make steel,

with iron making up most of steel. Nickel is added to give extra strength and

to give a shiny, protective coating.

Copper, Silver and Gold Group 11 Called “coinage metals” because they

were once used to make coins. (now most coins are made of nickel and

copper!) Copper used in electrical wiring Compounds containing silver help with

making photographs appear on paper. Silver and gold used in jewelry.

Zinc, Cadmium, and Mercury Group 12 Cadmium is used in rechargeable batteries Mercury- the only metal that is a liquid at

room temperature. Used in thermometers, thermostats, and batteries. Mercury is VERY poisonous!!!

The Inner Transition Metals Lanthanides and Actinides. Lanthanides #’s 58-71, named because

they follow the element Lanthanum (#57)

Actinides #’s 90-103, named because they follow the element Actinium (#89) All actinides are radioactive and unstable! Ex: Uranium used for nuclear energy.

Metals in the Earth’s Crust Metals are mined and then separated from

other rock.

Most platinum is located inSouth Africa.

Ores: Minerals and Mixtures Ore: made of a metal compound, or

mineral, within a mixture of clay and/or rock.

Process: Separate rock from mineral. Roasting- mineral converted to another

physical form-uses heat Metal refined into pure form.

Section 2: Nonmetals

Properties of Nonmetals Nonmetals are usually gases or brittle

solids at room temperature.

Nonmetals are not malleable or ductile. They do not conduct heat or electricity, they are not shiny.

Nonmetals are found to the right side of the periodic table (plus Hydrogen)

Elements in the Human Body

Bonding in Nonmetals Nonmetals can form ionic and covalent

compounds. Examples: textbook pg. 579

Pb + S = PbS

Hydrogen Hydrogen in it’s gas form is a diatomic

molecule: it consists of two atoms of the same element held together with a covalent bond. Example: H2

Hydrogen is VERY reactive. It has one electron and can combine with other elements to share the electron.

Halogens Group 17, includes F, Cl, Br, I, and At Seven valence electrons in outer energy

level.

Uses of Halogens Chlorine is used to disinfect pool water.

Iodine is a solid at room temperature and when heated changes directly to a gas: the process of sublimation!

The Noble Gases Stable because they have full outer energy

levels.

Section 3: Mixed Groups

Properties of Metalliods Metalloids share properties of both metals

and nonmetals. Metalliods also called SEMICONDUCTORS because they can conduct electricity better than nonmetals, but not as well as metals.

The Boron Group Group 13 Boron is a metalliod. Household items

that contain compounds of boron are borax (used in laundry detergent) and boric acid (insecticide).

Aluminum is the most abundant metal in earth’s crust,and is used in soft-drink cans, foil wrap, and to construct airplanes.

The Carbon Group Each element in group 14 has 4 valence

electrons. Carbon is a nonmetal and is found in coal, oil,natural gas, and foods.

Plants use carbon dioxide and sunlight to make glucose.

Continued…The Carbon Group Allotropes are different forms of the same

element. Example: Carbon: Diamond and Graphite

Semiconductors Silicon is the main component in

semiconductors, Germanium is also used Semiconductors: (elements that conduct an

electric current under certain conditions). Tin used to coat other metals to prevent

corrosion. Lead was once used in paints, but is no longer becauseit is toxic!

The Nitrogen Group Group 15- Each element has 5 valence

electrons. Nitrogen makes up 80% of the air we

breathe, and is the 4th most abundant element in our bodies.

Bismuth and Antimony are metals that are used in fire-sprinkler

heads because they helpto lower the melting points.

The Oxygen Group Group 16, Oxygen used by all living things to

breathe. Sulfur compounds used for pigments in

paints. Selenium needed in the body in VERY

small amounts, too much is toxic. Also used to make photocopies.

Synthetic Elements Scientists create elements by smashing

existing elements in a particle accelerator. Example: Smashing uranium with neutrons can

make neptunium. Neptunium atoms only last for about 2 days, and

when they disintegrate, they form plutonium.

Transuranium Elements Elements with more than 92 protons. They are synthetic, unstable, and many of

them disintegrate quickly.