Unit 1: Elements and compounds

Lesson 1: What are atoms and elements?

Atom

The smallest unit of an element that has the properties of that element.

Element

A substance made of only one kind of atom

Periodic Table

A table that shows the elements arranged by their atomic numbers

Compound

A substance made of two or more different elements

Molecule

A group of two or more atoms that are joined

Physical Property

A trait – such as color, shape, or hardness – that describes a substance by itself

Mixture

A combination of two or more different substances

Atoms and Elements

The smallest unit of matter is called an atom.

The simplest form of matter is called an element because it contains one type of atom.

Atoms are made of smaller particles such as protons, neutrons, and electrons. These particles are all alike.

The number of protons an atom has determines what element it is. Each type of atom has the properties of a certain element.

There are over 100 elements.

The Periodic Table

Elements are the building blocks of matter. The 100 elements combine to form millions of substances.

Atoms of each element have a certain number of protons. An atom’s atomic number is the number of protons it has. They are listed on a periodic table.

All elements on the left side (except hydrogen) are metals.

On the far right side are nonmetals. The color blue shows gases.

Molecules and Compounds

In nature, elements are rarely found in their pure form. They are mostly found in compounds, which are made of atoms from two or more elements.

A compound has a formula. Pure substances include elements

and compounds. In a pure substance, all particles are alike.

A molecule is the smallest unit of a compound that can exist in nature.

Sometimes, two atoms of the same element bond to form a molecule. This would include gases such as hydrogen, oxygen, and nitrogen.

Physical Properties

Physical properties are the traits that describe a substance.

A physical change is a change where a substance changes its state, but the substance remains the same.

Solubility is the ability to dissolve.

A mixture is when two or more substances combine and undergo a physical change when they mix, but they can be separated from the mixture.

A mixture where all the parts are mixed evenly is a solution.

Online Resources

Bill Nye – Atomshttp://www.youtube.com/watch?v=zbc85dv3ouk&feature=related

(Part 1 – 12:25)http://www.youtube.com/watch?v=uZ6zR0vu7cU&feature=related

(Part 2 – 9:36)- Making Molecules with Atoms (2:24)http://www.youtube.com/watch?v=qmgE0w6E6ZI