Atomic Structure

Atomic Structure

Objective NC Science 8.P.1.1

Getting the Idea

Everything around you is matter.

Matter is anything that has mass and volume.

Mass is the amount of matter in a substance.

Volume is the amount of space the substance occupies.

All substances--everything you own, everything you touch, event you yourself--are made up of different types of matter.

Multiple Choice

Which of the following is the best definition for matter?

• anything that has mass and volume

• the amount of space a substance occupies

• how much something weighs on earth

Atoms & Elements

Atoms are the basic building blocks of most of the matter around you. There are different kinds of atoms. Each kind of atom is an element. An element is one of the basic substances that combine to form all other substances. Elements cannot be broken down into simpler substances by ordinary chemical means.

Scientists have discovered about 118 elements. About 90 of these elements are found in nature. Carbon, oxygen, gold, silver, and iron are some naturally occurring elements. The remaining elements are synthetic, or made by humans in a laboratory.

Elements are pure substances. Pure substances are matter that has the same chemical composition throughout and cannot be separated into its parts by physical means.

Multiple Choice

True or False:

Atoms are the basic building blocks of most of the matter around you.

• true

• false

Atoms & their parts

An atom is the smallest particle of an element that has all the properties of that element. Each element is made up of atoms that differ from those of every other element. This diagram shows the structure of a carbon atom. Notice that this atom is made up of three different kinds of particles.

Multiple Select

Which of the following make up parts of an atom?

• neutron

• proton

• electron

• ultron

Atoms & their parts

The center of the atom is called the nucleus. The nucleus of most atoms is made up of two kinds of particles, protons & neutrons. Protons carry a positive (+) charge. Charge is an electrical property that can by either positive or negative.

Neutrons have no charge. The masses of protons and neutrons are measured in the atomic mass units (amu). Each proton or neutron has a mass of about 1 amu.

Electrons are subatomic particles that exist in an area outside the nucleus called the electron cloud. Electrons have a negative (-) charge. The mass of electrons is insignificant compared to the mass of protons & neutrons.

Multiple Choice

Which of the following parts of an atom are positively charged?

• neutron

• proton

• electron

• nucleus

The Electron Cloud

Within the electron cloud, electrons move in areas called energy levels. An energy level is a region in which electrons having similar amounts of energy are likely to be located. Electrons can absorb and release energy. This changes their location in the atom. If an electron gains energy, it moves farther from the nucleus. If an electron loses energy, it moves closer to the nucleus. Electrons can absorb or release energy in the form of light, heat, or other types of energy.

Multiple Choice

Which of the following parts of an atom can absorb or release energy in the form of heat, light, etc?

• Proton

• Neutron

• Electron

Elements & Subatomic Particles

The properties, or characteristics, of an element are determined by the structure of its atoms. The main difference between different elements is the atomic number. Atomic Number is the number of protons in the nucleus of an atom. The number of protons in the nucleus is unique for each element. Therefore, no two elements have the same atomic number. Carbon, for example, has six protons and an atomic number of 6.

Fill in the Blank

What measure does the Atomic Number show?

Elements & Subatomic particles

Look at the carbon atom on the right.➡️

Notice that the number of protons in the atom is equal to the number of electrons. Because these numbers are equal, each positive charge in the nucleus is balanced by a negative charge in the electrons around the nucleus. The atom as a whole is electrically neutral. If the numbers of protons and electrons in an atom are not equal, the atom has a charge. A charged atom is called an ion.

Multiple Choice

A charged atom is called a(n)...

• electron.

• ion.

• proton.

• acid.

Atomic Mass

Atoms have mass. The atomic mass of an atom is equal to the total mass of protons, neutrons, and electrons in the atom. Recall that each proton has a mass of about 1 amu. Each neutron also has a mass of 1 amu. Electrons have almost no mass. So you can find the atomic mass by counting the protons and neutrons in an atom.

This table give the atomic masses of some common elements. ➡️

Multiple Choice

Which of the following best describes atomic mass?

• the total mass of protons, neutrons, and electrons in an atom

• the code used to represent an element

• matter that is made up of the same chemical compostition and cannot be separated into parts by physical means

Atomic Mass

Notice the letters in parentheses beside the name of each element in the table. ➡️

These letters are the chemical symbol of the element. A chemical symbol is a code, normally composed of one or two letters, used to represent an element. Each element has its own chemical symbol. C always represents Carbon, Ca always represents Calcium, Fe always represents Iron, etc.

Multiple Choice

True or False:

A chemical symbol is a code used to represent each element.

• True

• False

Poll

How comfortable to you feel in your understanding of atoms and elements after this lesson?

• Very comfortable. I could pass the test today.

• Pretty comfortable, but I could use some more practice.

• Ok. I need some more study and practice.

• Not good. I am completely lost with this topic.