Lh Atoms - Teacher Notes

Life’s Hierarchy atom: An atom is the smallest part of a chemical element that has all the properties of that element. Examples of different atoms: Carbon, hydrogen, oxygen, nitrogen Picture: Oxygen Atom

Atoms that are missing or have extra neutrons are called isotopes. If you had very, very good eyes and could look at the atoms in a sample of hydrogen, you would notice that most of the hydrogen atoms would have no neutrons, some of them would have one neutron and a few of them would have two neutrons. These different versions of hydrogen are called isotopes. All isotopes of a particular element have the same number of protons, but have a different number of neutrons. If you change the number of neutrons an atom has, you make an isotope of that element.

History: 1808 John Dalton proposed his theory that all elements are made of atoms that cannot be divided or destroyed. John Dalton: is credited with proposing atomic theory which is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to obsolete beliefs that matter could be divided into any arbitrarily small quantity.

Dalton's Atomic Theory 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.

Ions are atoms with either extra electrons or missing electrons.

In electrically neutral atoms, the number of protons equals the number of electrons. Atoms remain intact in chemical reactions except for the removal, transfer, or exchange of certain electrons.