Elements and Atoms How far is an electron? Estimate the size of a dime That’s the nucleus How far away is the electron?

Matter: anything that has mass and takes up space. Elements: the simplest pure substances, and they cannot be broken down into any other substances.

Compound: a pure substance made of two or more elements that are combined chemically. Mixture: two or more substances – elements, compounds, or both – that are in the same place but are not chemically combined.

Atom: smallest particle of an element

Atomic Theory and Models Dalton’s Thomson Rutherford Bohr Cloud Modern

Dalton’s 1600 Sphere

Thompson 1897 Loaf of bread

Rutherford 1911 Gold foil experiment

Bohr’s -1913 Universe

Cloud of Electrons 1920 Cloud

Modern Atomic Model 1932 Neutron: electrically neutral and nearly same mass as a proton.

Homework Chose an element. Create a poster of at least three different atomic models (same element) Give information about the element and give information about the models and how they are different/similar 5 pts – Elemental information 5 pts – Model information 5 pts – Neatness and creativity

What is a phobia of chainsaws called?

Quiz: (2pts)Write two facts about a compound: (2pts)Write two facts about a mixture: (1pt) What is the difference between the Dalton and Thompson model of an atom?

Molecule Project DUE MARCH 19th (TUESDAY) Read the packet tonight and come back tomorrow with any questions. We will have some time in class to conduct research/work.

Atoms, Bonding, and the Periodic Table Valence Electrons: electrons that are in the highest energy level and held most loosely. This determines many properties of an element, including how they bond with each other.

The Periodic Table Symbol: 1 or 2 letters that represent an element. Atomic Number (#): the number of protons in the nucleus. Period: ROW of elements Group/Family: COLUMN of elements Atomic Mass: average mass PAGE 14-15 “Key”

Electron Dot Diagram: symbol of the element surrounded, each dot = one electron. Chemical Bond: the force of attraction that holds 2 atoms together.

Noble Gases: Group 18 elements, they have 8 valence electrons – except Helium and Hydrogen. Halogens: Group 17, they have 7 valence electrons. Alkali metals: Group 1, they have 1 valence electron.

Metals: react by losing electrons, especially when they combine with oxygen or a halogen. Nonmetals: 4 or more valence electrons. React when they gain/share electrons to have 8.

Metalloids: 3-6 valence electrons and can either lose or share electrons.

Ionic Bonds Ion: an atom or group of atoms that has an electric charge. When an atom loses an electron, it loses a negative charge and becomes positive. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Polyatomic ions: Ions that are made of more than one atom. Ionic Bonds: the attraction between two oppositely charged ions. Ionic bonds form as a result of the attraction between positive and negative ions. Ionic compound: a compound that consists of positive and negative ions.

Chemical Formulas and Names Chemical Formula: a combination of symbols that shows the ratio of elements in a compound. When ionic compounds form, the ions come together in a way that balances out the charges on the ions. Subscript: tells you the ration of the elements.

For an ionic compound, the name of the positive ion comes first, followed by the name of the negative ion.

In general, ionic compounds are hard, brittle crystals that have a high melting points. When dissolved in water or melted they conduct electricity.

Covalent Bond: chemical bond formed when two atoms share electrons. The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons. Molecule: neutral group of atoms joined by covalent bonds

Double Bond: two atoms share two pairs of electrons. Triple Bonds: three atoms share three pairs of electrons.

Molecular compound: a compound that is composed of molecules. Compared to ionic compounds, molecular compounds generally have lower melting points and boiling points, and they do not conduct electricity when dissolved in water.

Polar Bond: a covalent bond in which electrons are shared unequally Nonpolar bond: a covalent bond in which electrons are shared equally.