Atoms, Elements, Compounds

Elements Pure substance that cannot be broken down into other substances Made of only one kind of atom More than 100 naturally occurring elements Periodic table organizes the elements according to their properties

Periodic Table Atomic Number is equal to the number of protons in the nucleus of an atom of the element A row of elements is called a period A column of elements is called a group of family

Metals Most elements in the periodic table are metals (left of zig-zag line) Most metals are solids at room temperature Are good conductors of heat and electricity Are shiny (Luster) Are ductile ( can pulled into wires) Are malleable (can be bent without breaking)

Nonmetals Many are gases at room temperature Are not malleable Are not ductile Are not shiny Are poor conductors of heat and electricity Located to the right of the zig-zag line

Metalloids Have some properties of metals and nonmetal Are semiconductors Found along the zig-zag line

Atoms Smallest particle of an element that still has all the properties of an element Composed of three main types of particles (protons, neutrons, electrons)

Protons Positively charged particle Found in the nucleus Atomic number is equal to the number of protons in an atom

Neutrons No charge (are neutral) Also found in the nucleus of an atom Atomic mass is equal to the number of protons and neutrons in an atom

Electrons Negatively charged particle Move in the space outside of the nucleus Are arranged in energy levels

PEN P number of protons = E number of electrons = N atomic NUMBER

Let’s practice! Complete the chart. Element Atomic Number # of Protons # of Electrons Sodium 79 32 16 Tin

Check your answers ! Element Atomic Number # of Protons # of Electrons Sodium 11 Gold 79 Germanium 32 Sulfur 16 Tin 50

Label the elements in your chart as either metal, nonmetal, or metalloid.

Correct Labels Sodium is a metal Gold is a metal Germanium is a metalloid Sulfur is nonmetal Tin is metal (common sense!)

More Info… The atomic mass is equal to the number of protons and neutrons Unit = amu Amu = 1/12 the mass of a carbon-12 atom

Complete the chart! Atom # of protons # of neutrons Atomic mass 82 207 Krypton 48 31 Xenon

Correct Answers Atom # of protons # of neutrons Atomic mass Lead 82 125 207 Krypton 36 48 84 Gallium 31 39 70 Xenon 54 77 131

Periods Are equal to the number of energy levels

How many energy levels? Helium Sodium Radium Cesium

Correct answers… Helium = 1 energy levels Sodium = 3 energy levels Radium = 7 energy levels Cesium = 6 energy levels

Families and groups Similar structure Similar properties May correspond to the number of electrons in the last energy level (outer ring or shell)

Examples Sodium = 1 electron Potassium = 1 electron Oxygen = 6 electrons Tellurium = 6 electrons Xenon = 8 electrons

8 is the lucky number! Atoms are more stable if they have 8 electrons in their highest energy level. May combine together to make the number 8! (Becomes a compound!)

Example Sodium = 1 Chlorine = 7 Combine (1 + 7 = 8) Sodium Chloride or table salt

Compounds Forms when two or more different atoms combine Have properties that are different from those of the atoms from which they are made

Example Hydrogen is an explosive gas Oxygen is a gas that is needed to support a flame When chemically combined they form water which is used to put out most fires!

Molecular Compounds Form when different atoms share their outermost electrons Example – two atoms of hydrogen can share one electron with oxygen

Ions Forms when an atom or group of atoms gain or lose an electron Positive ion – loses electrons Negative ion – gains electrons

Ionic Compound Ions of opposite electric charges attract one another to form electrically neutral compounds Example - NaCl

Organic Compounds Always contain carbon and hydrogen Product of living things Examples – Carbohydrates, Lipids, Proteins, & Nucleic Acids

Inorganic Compounds Are made of elements other than carbon Examples of important inorganic compounds are water, calcium phosphate, hydrochloric acid, sodium bicarbonate, sodium chloride

Finding the number of atoms in a formula Example 1: C12H22O11 Write down the formula Place an arrow over each capital letter Write the symbol Write the name of the element Write the number of atoms for each element Add up the total amount of atoms

C12H22O11 C Carbon – 12 H Hydrogen – 22 O Oxygen – 11 Total = 12 + 22 + 11 Total = 45 atoms

Example 2 Ca(NO3)2 Ca Calcium – 1 N Nitrogen – 2 Oxygen – 6 Total = 1 + 2 + 6 Total = 9 atoms

Now you try! Pb(NO3)2

Pb(NO3)2 Pb Lead – 1 N Nitrogen – 2 O Oxygen – 6 Total = 1 + 2 + 6 Total = 9 atoms

Example 3: Coefficients! 4Al2(SO4)3 The large number 4 means 4 molecules of Aluminum Sulfate or 4 times everything!

4Al2(SO4)3 Al Aluminum – 8 S Sulfur – 12 O Oxygen – 48 Total = 68 atoms!

You try! 2Mg(C7H5O3)2

Solution 2Mg(C7H5O3)2 Mg Magnesium = 2 C Carbon = 28 H Hydrogen = 20 O Oxygen = 12 Total = 62

Now, balancing chemical equations!

Is it balanced? If not, balance the following!

HCl + KOH  KCl + H2O

It is balanced!!!!!!

Al + S8  Al2S8

Answer 2Al + S8  Al2S8

H3PO4 + Ca(OH)2  Ca3(PO4)2 + H20

2H3PO4 + 3Ca(OH)2  Ca3(PO4)2 + 6H2O

K + O2  K2O

Answer 4K + O2  2K2O