Chapter 4 Study Sheet Atomic Theory for 6th Graders

Matter is anything that has mass and takes up space.

Who’s that guy?? Lavoisier is the scientist who introduced the law of conservation of matter. It says that matter is neither created nor destroyed, but only changes form.

John Dalton is a scientist who developed a model called the atomic theory of matter. It said that atoms are too small to be seen by the human eye and that each type of matter is made of only one kind of atom.

J.J. Thomson is a scientist who conducted experiments with a cathode ray tube, and discovered invisible negatively charged particles called electrons.

Ernest Rutherford is a scientist who did experiments with gold foil and discovered that atoms had a central part called a nucleus and that in there are positively charged particles caled protons, He also discovered that an atom is made up mostly of empty space.

A scientist named James Chadwick discovered that the extra mass in atoms were due to neutrally charged particles in the nucleus called neutrons.

In the modern atomic model, we know that electrons do not orbit around the nucleus like Jimmy Neutron’s logo. Instead, they move in what is called the atom’s electron cloud.

Elements are made up of only one kind of atom. There are 115 known elements. 90 of them occur naturally.

The Periodic Table is sorted by atomic number, which tells how many protons are in the nucleus of the element’s atoms.

Some elements have atoms with different number of neutrons in their nucleus. These are called isotopes.

When you add the number of protons and neutrons together, you get the mass number.

The number found below the element symbol on the periodic table, which is the weighted average mass of all the isotopes of the element, is the atomic mass.

Metals have a shiny or metallic luster and are good conductors of heat and electricity. Most metals are solids at room temperature. Metals are malleable, which means they can be shaped. Metals are also ductile, which means they can be drawn into wires without breaking.

carbon Sulfur Non metals are usually dull in appearance. Most are poor conductors of heat and electricity. Many are gases at room temperature. Solid nonmetals are generally brittle, meaning that cannot change shape easily without breaking. 97% of the human body is made of of non metals.

Metalloids have characteristics of both metals and nonmetals Metalloids have characteristics of both metals and nonmetals. They do not conduct heat and electricity as well as metals. All metalloids are solids at room temperature.

A substance is matter that has the same composition and properties throughout. A compound is a substance whose smallest unit is made up of atoms of more than one element.

A chemical formula tells which elements make up a compound as well as how many atoms of each element are present. H20 = 2 atoms of hydrogen and 1 atom of water

A subscript number (the tiny number written below and to the right of each element’s symbol) tells how many atoms of that element are in the compound. C6H12O6= 6 carbon 6 hydrogen 6 oxygen No subscript number is used when only one atom of the element is present. CO2 = 1 carbon 2 oxygen

A given compound is always made of the same elements in the same proportion (ratio). For example…in water (H20) You will always have twice as many hydrogen molecules as oxygen, whether you have a drop or an ocean full.

A mixture is two or more substances mixed together which don’t make a new substance.

Unlike compounds, the proportions of the substances in a mixture can be changed without changing the identity of the mixture. What if you had more crunchberries in your Captain Crunch? Would it still be Captain Crunch?

In a mixture, you can separate the different substance from each other.

There are two different kinds of mixtures. In a homogeneous mixture, they are the same throughout. In a heterogeneous mixture, you can see the different parts.