Bohr Model Energy levels How can I draw the electron cloud of the elements by looking at the atomic number?

Valence Electrons We look at atomic number to see the number of protons (and electrons, because the atom must be stable). The electrons they occupy the highest energy level of an atom. The outermost energy level is called the valence shell. Valence electrons play a key role in the chemical properties of an element.

-Niels Bohr’s Model – Distinct Energy Levels

Valence Electrons In the first ring= up to 2 electrons Once you fill up of the 2 electrons, move to the second ring. In the second ring= up to 8 electrons In the third ring= up to 8 electrons

Energy Shells Each energy shell/level is represented by a circle around the nucleus of the atom. The first (lowest) energy level holds only 2 electrons After this level is filled up, electrons go to a higher (outer) E level. Electrons fill the lower levels and then move to higher (outer) levels. (No matter how many energy levels there are, the outermost energy level can only hold at most 8 electrons)

Energy Shell Example Carbon: What is its symbol? What is the atomic number? What is the atomic mass? How many protons does it have? How many electrons does it have? How many neutrons does it have? How many electrons go in the first shell? How many electrons go in the next shell? How many valence electrons are there?

Energy Shell Example Carbon: What is its symbol? C What is the atomic number? 6 What is the atomic mass? 12 How many protons does it have? 6 How many electrons does it have? 6 How many neutrons does it have? 6 How many electrons go in the first shell? 2 How many electrons go in the next shell? 4 How many valence (last shell) electrons are there? 4

Let’s try building Silicon Atom Model.

Let’s try building Oxygen Atom Model.

Modern Periodic Table

Part I Introduction. Periods and groups. Metals, nonmetals and metalloids.

The Modern Periodic Table The Periodic Table is a listing of all the known elements, developed by Dmitri Mendeleev. The elements are organized by: Atomic number Chemical Properties

How do you read the PERIODIC TABLE?

Groups and Periods Group( or Family): a vertical column. Elements in groups have similar chemical properties. There are 7 Groups/ column. Period: a horizontal row. There are 18 numbered rows.

Metals, Nonmetals and Metalloids Elements can be classified into: Metals Nonmetals Metalloids (semimetals)

Nonmetals Metals Metalloids

Physical Properties of Metals Most elements are metals Good conductors of electricity and heat. Malleable (can be hammered into sheets). Ductile (can be drawn into wires). Most metals are solid at room temperature Example: Lithium/ Iron

Chemical Properties of Metals Easily lose electrons. Form positive (+) ions.

Nonmetal Physical Properties More than half of nonmetals are gas at room temperature Nonmetals are not ductile or malleable Nonmetals are poor conductors Examples: Oxygen/ Carbon

Nonmetal Chemical Properties Gain electrons. Form negative ions.

Metalloids Metalloids have some properties of metals and some properties of nonmetals Metalloids are also called semiconductors because they conduct electric current better than nonmetals but not as well as metals. Example: Boron and Aluminum

Isotopes Different versions of the same element. Elements can be an Isotope when it has a more or less neutrons. Same Atomic Number (# of protons) Different Atomic Number (# of protons + neutrons). Because the # of neutrons are different.