Chapter 18 Properties of Atoms and the Periodic Table

Objectives: Discuss chemical symbols

Describe the atomic components.

Discuss and describe quarks.

Discuss models.

Describe the history of the atomic model.

A chemical symbol is an abbreviated or scientific shorthand of writing an element’s name.

A chemical symbol is either a capital letter or a capital letter followed by a lower case letter.

Examples: C Ca Al He

Not: c ca al AL HE

An atom is the smallest piece of matter that maintains its properties.

Protons are found in the nucleus with a +1 charge.

Neutrons are found in the nucleus with no charge.

Electrons are found outside the nucleus in the electron cloud with a -1 charge.

Electron cloud is made up of electrons.

Nucleus is made up of protons and neutrons.

Electrons are not composed of smaller particles.

Electrons are fundamental.

Protons and neutrons are made of smaller particles called quarks.

There are six types of quarks: top, bottom, up, down, strange, charm.

The Tevatron is used to accelerate particles and collide them to produce tracks to study quarks.

Study and learn Table 5.1 on page 544.

A model is a visualization of something that is hard to see.

A scaled up model is a big-scale representation of something small ex: cell, atom

A scaled down model is a small-scale representation of something big ex: solar system, planes, cars.

The atomic model started as a solid sphere from Democritus.

The atomic model today is the electron cloud model which shows a positively charged nucleus surrounded by an electron cloud.

Study the atomic models on page 548.

Democritus 400 BC atomos “uncuttable” solid sphere

John Dalton 1800’s atomic theory (3 parts) solid sphere

J. J. Thomson 1904 Plum Pudding Model solid sphere with negative particles embedded

Ernest Rutherford 1911 solid sphere with electron orbiting

Neils Bohr 1913 “Jimmy Neutron model” nucleus (protons and neutrons) with electrons orbiting

Electron Cloud Model 1926 nucleus (proton and neutrons) surrounded by an electron cloud which shows the

probable location of the electron

Objective: Compare the masses of the atomic components.

Identify common isotopes.

Calculate the average atomic number, mass number, number of protons,

neutrons, and electrons.

The neutron is the largest atomic component, followed by the protons.

The electron is the smallest atomic component.

The atomic number is the number of protons in an element.

The number of protons determines the identity of an element.

The number of electrons (negative) is equal to the number of protons (positive) to balance the element out.

The number of neutrons is equal to the mass number minus the atomic number.

An isotope is the same element with a different number of neutrons.

The average atomic mass is closest to the most abundant isotope.

Objective: Explain the history of the periodic table.

Differentiate between groups and periods.

Use the periodic table to obtain information.

Classify elements as metals, nonmetals, and metalloids.

Periodic means repeating in a pattern.

The periodic table is an arrangement of elements in a pattern.

Dmitri Mendeleev created the first periodic table.

It was arranged by increasing atomic mass.

Henry G.J. Mosely changed the periodic table to the one used today.

Today’s periodic table is arranged by increasing atomic number.

A vertical column (top to bottom) on the periodic table is called a group or family.

Groups are made of elements with similar properties.

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

Each of the seven energy levels can have a maximum number of electrons in the outer level.

Energy levels closer to the nucleus have lower energy than ones farther away.

Energy level one can contain at most two electrons.

Energy level two can contain at most eight electrons.

The maximum number of electrons per level is 2n².

Each row in the periodic table ends when an outer energy level is filled.

Electron dot diagrams or Lewis symbols use the elements’ symbols and dots to represent outer energy level electrons.

Periods are horizontal rows of elements with increasing numbers of protons and electrons.

Elements are classified as metals, nonmetals, and metalloids or semimetals.

Metals are usually shiny, good conductors of heat and electricity, and solids at room temperature.

Nonmetals are usually dull, poor conductors of heat and electricity, and gases at room temperature.

Metalloids or semimetals have properties of metals and nonmetals and are good semiconductors.

Metals are located to the left of the stair-step line.

Metalloids are semimetals are located along the stair-step line.

Nonmetals are located to the right of the stair-step line.