DO NOW October 31, 2014 Do the following in your CNB. 1.Get your worksheet out and work on it!!!

DO NOW October 30, 2014 Do the following in your CNB. 1.Complete the following information for Element 4: Atomic Number Chemical symbol Element name Atomic Mass Mass number Protons Neutrons Electrons

Atomic Structure and The Periodic Table Introduction to Atomic Structure:

Atom Structure Atoms have: A nucleus Center, small, heavy part of the atom. The mass comes from here. Contains protons (+) and neutrons (0). An electron cloud Large, lightweight part of the atom. Contains the electrons (-)

Atom Structure Protons + charge Neutrons 0 charge Electrons – charge. Atom Structure

The periodic table went through a series of changes just like the model of the atom. Dmitri Mendeleev was one of the first ones to study the properties of the 63 known elements. He created the first periodic table in Mendeleev noticed that some elements had similar chemical properties and physical properties. Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass. He found that the properties repeated regularly. As he organized them, Mendeleev noticed that elements in the same group/families shared similar properties.

As scientists discovered new elements and learned more about the atom, the periodic table changed. The modern periodic table of the elements is arranged by order of increasing atomic number. The periodic table is organized in rows called periods and columns called groups. Groups are also called families. An element’s properties can be predicted from its location in the periodic table. From left to right, the properties of the elements change in a pattern. Elements in the same group/families share similar properties.

7 18 Rows Columns

Elements in the same group are known as families because They share similar chemical and physical properties. Group 1 - Alkali Metals. (except of Hydrogen which is a nonmetal gas) Group 2 – Alkaline Earth Metals. Groups 3-12– Transition Metals. The two lines below – Inner Transition metals. The top is the Lanthanides and the bottom one is the Actinides. Group 17 – Halogens Group 18 – Noble Gases

Atomic number Number of protons in the nucleus. It tells what element it is. Chemical symbol Name of the element. Average Atomic mass an average of all of masses of the isotopes of that element.

Chemical Symbol Each element has its own name, accompanied by a chemical symbol. Usually one or two letters (first is always capitalized).

 The atomic number identifies the element.  It equals the number of protons found in the nucleus of the atoms of the element.  Every atom of the same element has the same number of protons.

 The number of protons of the atom is given by the atomic number.  You can find this information in the periodic table.

 Atoms are electrically neutral.  This means that the number of electrons (-) equals the number of protons (+).  Since the atomic number equals the number of protons then it also equals to the number of electrons in an atom. This is Lithium Atomic number 3 Has: 3 protons 3 electrons

 The average atomic mass is the number found under the symbol.  Usually a decimal because it is an average of the masses of the isotopes of that element.

 Some atoms of the same element have different masses. This is due because they have different number of neutrons.  Atoms of the same element that have different number of neutrons are called isotopes.  Isotopes are different versions of the same element.  Most elements consists of a mixture of isotopes. Remember that the mass of the atom comes from the nucleus which contains the protons and the neutrons. Electrons are considered “weightless”.

Average atomic mass and Isotopes Exploration: Cl has two isotopes Cl and 35 Cl

99% of all carbon atoms are the isotopes containing 6 neutrons, the remaining 1% is the heavier isotope containing 7 neutrons, which raises the average mass of carbon from to

Isotope Cont. Example:

 Remember that the mass of an atom comes from its nucleus (protons and neutrons).  To find the number of neutrons, the mass number is needed.  The mass number equals to the number of protons plus neutrons in the nucleus of an atom.  To get the mass number, round the average atomic mass to a whole number.  To find the number of neutrons, subtract the number of protons from the mass number. This is Lithium, 3 protons Mass number = 7= 3P + 4 N Remember that the number of protons is given by the atomic number. Mass Number – Atomic Number = number of neutrons

 To find the number of neutrons, subtract the number of protons from the mass number.  Remember that the number of protons is given by the atomic number. Mass number = = 4 4 Neutrons 3 Protons 3 Electrons Mass Number – Atomic Number = number of neutron

3 Protons 3 Neutrons Mass number 6 3 Protons 4 Neutrons Mass number 7

Elements in the same group are known as families because They share similar chemical and physical properties. Group 1 - Alkali Metals. (except of Hydrogen) Group 2 – Alkaline Earth Metals. Metals in the center – Transition Metals. The two lines below – Inner Transition metals. The top is the Lanthanides and the bottom one is the Actinides. Group 17 – Halogens Group 18 – Noble Gases

An isotope is identified by its mass number, which is the sum of the protons and the neutrons in the atom The symbol X represents the element symbol. The mass number A: equal to the number of protons and neutrons in the isotope (placed as a left superscript). The atomic number Z: equal to the number of protons (placed as a left subscript). A= Z + N, where N is the number of neutrons.

Practice writing the isotopic symbol

Each element has a different atomic structure consisting of a specific number of protons, neutrons, and electrons. The number of protons and electrons is always the same for a neutral atom of a given element. Element Structure Why do atoms combine?

This neutral lithium atom has three positively charged protons, three negatively charged electrons, and four neutral neutrons. Element Structure Why do atoms combine?

The different areas for an electron in an atom are called energy levels. Electron Arrangement— Electron Energy Why do atoms combine?

The farther an energy level is from the nucleus, the more electrons it can hold. Number of Electrons Why do atoms combine? The first energy level, energy level 1, can hold one or two electrons, the second, energy level 2, can hold up to eight, the third can hold up to 18, and the fourth energy level can hold a maximum of 32 electrons.

The stairway, shown here, is a model that shows the maximum number of electrons each energy level can hold in the electron cloud. Energy Steps Why do atoms combine?