Intro to Chemistry Chemistry PowerPoint # 1

Blind Men and the Elephant Click here to read

Element Element – a substance that cannot be broken down into another substance by chemical or physical means.

Atom Atom – the basic unit of matter, the smallest particle of an element. – Nucleus – Electron cloud

Element Song Make sure speakers are hooked up and volume is up! Click here to watch

Dmitri Mendeleev 1869, Russian scientist Recognized hidden patterns in the elements Similar chemical and physical properties

Dmitri Mendeleev Recorded two important facts 1.Atomic Mass 2.Bonding Power Mendeleev arranged first periodic table by atomic mass.

Periodic – a regular repeated pattern

Periodic Table Periodic Table – chart of elements showing repeating pattern of their properties

In the nucleus of an atom Nucleus – core of the atom – Proton – positively charged particles in the nucleus – Neutron – uncharged particle in the nucleus

Outside the nucleus of an atom Electrons – negatively charged particles outside the nucleus. – Move constantly and rapidly around nucleus – 2000 times less the mass of a proton Activity

Weight? Parts of an atom are so small they created their own unit of measurement… AMU or Atomic Mass Unit 1 AMU = weight of 1 proton

Mass vs. Weight Mass = the amount of space an object occupies Weight = based on the amount of gravitational pull on an object Ex. An astronaut on the moon has the same mass as on earth, but their weight is different.

Atomic Mass Atomic Mass – the average mass of one atom of the element. – Most of the mass of an atom is in the nucleus. – Difference due to different # of neutrons in the nucleus. Activity

Atomic Number Atomic Number – number of protons in the nucleus. – Unique property that indentifies an element – Constant for all atoms of an element – Periodic table is now organized by atomic number

Reading the periodic table

Element Symbol Element Symbol – 1 or 2 letters representing the element. – First letter capitalized, second letter lowercase O He Fe Si C N P Al Cl

Organization of the Periodic Table Today – arranged by atomic number Element property determined by location on PT

Group/Family Group – elements in the same vertical column of the periodic table. 18 total groups

Specific Groups Elements in each group have similar characteristics. Group 1 – react violently with water Group 11 – elements react slowly with water Group 18 - rarely react at all

Period Period – each horizontal row across the periodic table. Properties are not alike Gradually change properties as you move Left to Right. More reactive on left, Inactive gas on right. 7 total periods

Calculating Protons and Electrons Atoms have a neutral overall charge, meaning # of protons = # of electrons Element = Atomic Number = # of protons = # of electrons Fe = 26 (atomic number) = 26 protons = 26 electrons Pb = 82 (atomic number) = 82 protons =82 electrons

Give it a try Element = atomic number = protons = electrons Au = __________ = 79 = _____ Ta = 73 = _______ = ________ ______ = ________ = _________ = 53 ______ = 70 = _______ = _________ Pa = _______ = ________ = ________

Calculating neutrons (Rounded Atomic Mass) – (atomic #) = # neutrons 1.Round the atomic mass to the nearest whole # 2.Subtract the atomic number from the atomic mass 3.This number equals the number of neutrons Ex. Mercury (Hg) Atomic Mass = Atomic Number = – 80 = 121 neutrons

Give it a try (Rounded Atomic Mass) – (atomic #) = # neutrons Be ________ - 4 = 5 neutrons V 51 – 23 = ______ neutrons Rh ______ = 58 neutrons Ar _______ - 18 = _______ neutrons Ga _______ - ______ = _______ neutrons

Valence Electrons Valence Electrons – electrons available to be lost, gained, or shared in the formation of chemical compounds. Furthest from the nucleus. Electrons are in layers, only the outer layer can be shared or transferred (valence electrons)

Valence Electrons Group NumberNumber of Valence Electrons or