Atoms and the Periodic Table

Chapter 4

Families of ElementsSection 3

The Periodic table groups similar elements together to make it easier to predict the properties of an element based on its location.

How is the Periodic Table organized?◦ Based on the number of protons, or atomic

number, an element has in the nucleus of an atom.

Organization of the Periodic Table

Periodic Law◦ States that the repeating chemical and physical

properties of elements change periodically with the atomic numbers of the elements.

Periods◦ Horizontal rows of elements in the Periodic Table.

Groups◦ Vertical columns of elements in the Periodic Table.

Organization of the Periodic Table

How Are Elements Classified?Figure 22 B, Page 120

Metals◦ An element that is lustrous, ductile, malleable and conducts

heat and electricity well. Lose electrons to form cations.

Nonmetals◦ An element that conducts heat and electricity poorly.

Can be solids, liquids or gases. Solids are typically dull and brittle. Gain electrons to form anions.

Metalloids◦ An element or compound that conducts electric current better

than an insulator but not as well as a conduct does.

How Are Elements Classified?

Alkali metals◦ The elements in Group 1 on the Periodic Table.◦ Soft and shiny◦ React violently with water.http://www.youtube.com/watch?v=uixxJtJPVXk

Why do these metals react so violently?

Metals

Alkaline-earth◦ Group 2 elements on the Periodic Table.◦ Still react with water, but not violently.

◦ Calcium compounds Used for construction “skeletons” of animals Strength for teeth and bones.

Metals

Transition Metals◦ Elements from groups 3-12 of the Periodic Table.

Actinides and Lanthanides◦ Located below the Periodic Table◦ Lanthanides are also considered Rare Earth

Metals, along with scandium and yttrium. Essential to medical diagnosis equipment and almost

all military systems. Critical components for modern electronic technologies.

Metals

All metals conduct heat and electricity. They are all ductile, malleable and lustrous. Most metals can be stretched and shaped

into flat sheets or pulled into wires.

Radioactive◦ The nuclei of the atoms are continually decaying to

produce different elements.◦ Elements with atomic number greater than 92 are

man-made, and from 84 and greater are radioactive.

Metals

Carbon◦ Graphite, pencil lead◦ Diamonds◦ Sugar, or glucose◦ Chlorophyll◦ Fullerenes

Oxygen and Nitrogen are the most plentiful gases in the air we breathe.

Nonmetals

Halogens◦ Group 17 on the Periodic Table.

Chlorine protects you from harmful bacteria.◦ In gas form, it is a poisonous yellowish green gas

that consists of two chlorine atoms bonded together, Cl2.

Fluorine is a poisonous yellowish gas. Bromine is a dark red liquid. Iodine is a dark purple solid.

Nonmetals

Diatomic Gases◦ Made up of two atoms

There are 7 diatomic atoms:◦ Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine,

Bromine, and Iodine.◦ H2, N2, O2, F2, Cl2, Br2, and I2

Nonmetals

How Are Elements Classified?Figure 22 B, Page 120

Noble Gases◦ Group 18 on the Periodic Table.◦ The gases are inert.◦ Found as single atoms in nature, not molecules.

Nonmetals

Nonmetals

Figure 31, Page 127

Metalloids◦ An element or compound

that conducts electric current better than an insulator but not as well as a conductor. Nonmetals that have some

properties of metals. Found along the stair-

step line. 7 metalloids:

◦ Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, and Polonium.

◦ B, Si, Ge, As, Sb, Te, Po

Boron◦ Extremely hard, added to steel to increase hardness

and strength at high temperatures. ◦ Often used for heat-resistant glass.

Arsenic◦ Shiny solid that tarnishes when exposed to air.

Antimony◦ Bluish white brittle solid that shines like a metal.◦ Found in fire retardants.

Tellurium◦ Is a silvery white solid whose ability to conduct

increases slightly with exposure to light.

Nonmetals - Metalloids

Silicon◦ Accounts for 28% of the mass of the Earth’s crust.◦ Sand, silicon dioxide: SiO2.◦ Computer chips, transistors, LED display screens,

and solar cells.◦ Impurities increase ability to conduct electricity.

Nonmetals - Metalloids

A Guided Tour of the Periodic Table

Section 2

Ionization◦ An atom gains or loses valence electrons in order

to have a full outermost ‘s’ and/or ‘p’ orbital.

When atoms gain or lose electrons, the atom is no longer neutral.

Ion◦ An atom or group of atoms that has lost or gained

one or more electrons, has a negative or positive charge.

Some Atoms Form Ions

Cation◦ Positively charged ion that has lost an electron.

All metals are cations.

Anion◦ Negatively charged ion that has gained an

electron. All nonmetals are anions.

Some Atoms Form Ions

Atomic number, Z◦ The number of protons in the nucleus of an atom.◦ The atomic number never changes for a given

element.

Mass number, A◦ the sum of the numbers of protons and neutrons

in the nucleus of an atom.

How Do the Structures of Atoms Differ?

Isotope◦ An atom that has the same number of protons as

other atoms of the same element do but has a different number of neutrons.

Hyphen notation◦ The name of the element, hyphen, and then the

mass number of the isotope.

How Do the Structures of Atoms Differ?

Isotopes of Hydrogen◦ Protium-1◦ Deuterium-2◦ Tritium-3

How Do the Structures of Atoms Differ?

Isotope Atomic Number

Mass Number

Protons

Electrons

Neutrons

Protium 1 1 1 1 0Deuterium 1 2 1 1 1

Tritium 1 3 1 1 2

Finding the number of Neutrons:

◦ Mass Number – Atomic Number = Number of Neutrons

◦Example: Oxygen-18

How Do the Structures of Atoms Differ?

Average Atomic Mass◦ The weighted average of the masses of all

naturally occurring isotopes of an element.

Using average atomic mass, round to nearest whole number to find the mass number.

Atomic Mass unit (amu)◦ A unit of mass that describes the mass of an

atom.

How Do the Structures of Atoms Differ?

Atomic StructureSection 1

What are atoms?◦ Tiny particles that determine the properties of all

matter.◦ Translates to “unable to be divided”.◦ The smallest part of an element that maintains

that element’s properties. Who was Democritus?

◦ A Greek philosopher who believed the movements of atoms caused the changes in matter that he saw.

What are Atoms?

John Dalton◦ An English school teacher who developed his own

atomic theory that formed the foundation for the modern atomic theory.

Dalton’s Atomic Theory:◦ Atoms of different elements can join to form

compounds. ◦ All atoms of a given element are exactly alike.◦ Atoms cannot be divided.

Are the last two assumptions true?

What are Atoms?

What’s in an Atom?

Table 1, Page 106

Atoms can actually be divided into smaller particles. What are the particles?◦ Proton- subatomic particle

that has a positive charge, found in the nucleus.

◦ Neutron- subatomic particle that has no charge, found in the nucleus.

◦ Electron- subatomic particle that has a negative charge, found outside the nucleus in the electron cloud.

Electrons are about 2000 times smaller than a proton and a neutron.

Nucleus- center of an atom where the protons and neutrons reside.

Electron cloud- the area where the electrons orbit around the nucleus of an atom.

Do atoms have a charge?

What’s in an Atom?

Models have been adapted as new information has been discovered.

Niels Bohr suggested that:◦ Electrons move in set paths around the nucleus.◦ Each electron has a certain energy, and the path

defines the electrons energy level.

Models of the Atom

Models of the Atom

Figure 5, Page 107

How can electrons move from one energy level to another?

Absorption- ◦ the take in of energy.

Emission- ◦ the release of energy.

Bohr’s model no longer explains electrons behavior, but helps in understanding energy levels.

Do not orbit in definite paths.

In the current model of the atom, electrons move like waves.

Models of the Atom

Heisenberg Uncertainty Principle◦ Cannot predict where an electron is located and

the speed at the same time.

We can calculate the chance of finding an electron at a certain location.

Models of the Atom

Models of the Atom

Figure 7, Page 108

Each energy level can have a certain number of electrons.

Can determine energy level by a simple equation: 2n2.

In each energy level, there are certain “orbitals” that the electrons can be found in.

Valence electrons-◦ Electron(s) that are found in the outermost shell

of an atom.◦ Valence electrons determine the atom’s chemical

properties and its ability to form bonds.

How many valence electrons can an atom have?

How can we determine valence electrons in an atom?

Models of the Atom

Orbitals-◦ The regions in an atom where electrons are going

to be found 90% of the time.

There are four different orbitals.◦ S, p, d, and f

Each orbital can be occupied by a total of two electrons.

Models of the Atom

Models of the Atom

Figure 8, Page 109

The ‘s’ orbital

The lowest energy occupied orbital.

There is only one orbital for ‘s’.

Spherically shaped.

Models of the Atom

Figure 9, Page 109

The ‘p’ orbital

There are three orbitals for ‘p’.

The ‘p’ orbital can have a total of 6 electrons.

This orbital has a dumbbell shape.

The ‘d’ and ‘f’ orbitals are more complex than ‘s’ and ‘p’.

The ‘d’ orbital has 5 orbitals and can hold a total of10 electrons.

The ‘f’ orbital has 7 orbitals and can hold a total of 14 electrons.

Models of the Atom

Location of the orbitals

Electron configurations-◦ The arrangement of electrons in the orbitals.

‘d’ orbitals have a lower coefficient than ‘s’ and ‘p’ when written.

How do we write them?

Models of the Atom

Noble Gas Configuration◦ The short hand way of writing electron

configurations.◦ Take the noble gas that comes before the element

that the configuration is being written for. ◦ Put the noble gas in brackets [ ].◦ Write the rest of the configuration like normal.

Models of the Atom