How are atoms studied? Atoms are the building blocks of matter Atoms are too small in size to study easily Size of Earth : soda can = soda can : atom

Democritus Not until around 460 B.C., did a Greek philosopher, Democritus, develop the idea of atoms. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms.

Democritus He said in the world this was “atoms and void”. No space between the atoms.

ATOMS Atoms: smallest particle that matter can be broken down.

Who studied the atom? Studied by many scientists for centuries –Democritus (400 BC) – phrase “atomos” –Rutherford (1911) – nucleus (gold foil expt) –Moseley (1913) – X-rays to find atomic # –Bohr (1913) – planetary model of the atom –Schrödinger (1923) – electron cloud model

Thomson’s Plum Pudding Model In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles.

Thomson Model He proposed a model of the atom that is sometimes called the “Plum Pudding” model. Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding.

Atoms, Molecules and Ions 1806 Atomic Theory of Matter 1. Matter consists of indivisible atoms 2.All atoms of a given element have identical properties 3.Different elements have atoms that differ in mass 4. Atoms are indestructible and chemical reactions are a rearrangement of atoms 5. Compounds contain a definite and small number of atoms John Dalton

Discovery of the Atom By the early 1800’s, John Dalton proposed that all substances are made up of atoms. In 1898, J.J. Thomson, proposed that atoms are made up of smaller parts. In 1911, Ernest Rutherford, proposed that atoms have electrons and a positive charged nuclues.

Parts of an Atom 1.Proton - nucleus 2.Neutron – nucleus 3. Electron – shells Protons and neutrons make up the nucleus and has the most mass. Electrons do not weigh as much.

Protons Protons are located in the nucleus of the atom. They are positively charged.

Neutrons Neutrons are located in the nucleus. They have NO charge!

Electrons Electrons are located in the shells around the atom. They are negatively charged. Ion – a charged atoms caused by the loss or gain of an electron.

Atoms make up substances called elements which are the building blocks of matter. There are 110 elements

1. ELEMENTS ARE PURE SUBSTANCES MADE OF ONLY 1 KIND OF ATOM AND ARE THE BUILDING BLOCKS OF MATTER. 2. ELEMENTS CANNOT BE BROKEN DOWN INTO A SIMPLER SUBSTANCE 3. ELEMENTS HAVE THEIR OWN UNIQUE SET OF PROPERTIES THAT NO OTHER ELEMENT HAS.

ELEMENTS ARE MADE OF ONLY 1 KIND OF ATOM SOME COMMON ELEMENTS –HYDROGEN (H), HELIUM (He), OXYGEN (0), –Notice that the first letter is capital and the next letter is lower case.

Why Do Some Elements Have Different Symbols? They are older elements that were name in a different language like Latin. Copper – cuprum Iron – Ferrous Gold - aurum Silver - argentum

Elements in Organisms 4 elements that make up 96% of human body: Carbon(C), Hydrogen(H), Oxygen(O), Nitrogen(N)

Element Info in Each Box Atomic weight Atomic Number Symbol Name

Information from the periodic table Atomic Number- Number of Protons in an atom Silver = 47 protons

Atomic Weight - total number of particles in an atom's nucleus Atomic Weight is not very helpful – you need to find the atomic mass

To find the Atomic Mass: Round the atomic weight Krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84. Mass Number = (Number of Protons) + (Number of Neutrons) 84 =

1. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE ACCORDING TO ATOMIC NUMBER Ways the Periodic Table is Organized

2. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE OF ELEMENTS ACCORDING TO THEIR SIMILAR CHARACTERISTICS 3 major groups: metals, nonmetals and metalloids

Arrangement of the Periodic table 3.Periods – Rows are called periods. The Elements in these rows have the same number of electron shells. 4. Groups – Columns are called groups. These elements have the same properties because of the number of valence electrons.

Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different period (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of electron shells. Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.

Groups When a column goes from top to bottom, it's called a group. Groups are often called families because these elements seem to be related. **Elements in the same group show similarities in their chemical and physical properties.

Electron shells a)Atomic number = number of Electrons b)Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. c)Electron shells determine how an atom behaves when it encounters other atoms

VALENCE ELECTRONS Number of electrons in the outermost. Determines how the element will bond. GROUPS: determined by valence electrons. Group 1 – one valence electron Group 2 – 2 valence electrons

Valence Electrons The number of valence electrons determines how an atom will bond. The behavior of an atom is determined by its electrons. Shell Numb er Maximum Number of Electrons in the Shell 12 x 1 = 2 22 x 4 = 8 32 x 9 = x 16 = x 25 = 50

Determining the valence electrons for some elements Li – 3 electrons 2 e- in 1 st level 1 e- in 2 nd level 1 valence electron C – 6 electrons 2 e- in 1 st level 4 e- in 2 nd level 4 valence electrons

Timberlake, Table 2.15 (7 th Ed); Table 2.14 (8 th Ed)

How do you calculate Valance Electrons? You determine the number of electrons. Then place the electrons in electron shells. Bohr’s Model: This is a model used to place electrons in their shells.

Bohr Diagrams 1)Find your element on the periodic table. 2)Determine the number of electrons – it is the same as the atomic number. 3)This is how many electrons you will draw. 4)The number of shells are determined by the period.

Bohr Diagrams Find out which period (row) your element is in. Elements in the 1 st period have one energy level. Elements in the 2 nd period have two energy levels, and so on.

Bohr Diagrams C C 1)Draw a nucleus with the element symbol inside. 2)Place Protons and neutrons in the nucleus. 3)Carbon is in the 2 nd period, so it has two energy levels, or shells. 4)Draw the shells around the nucleus.

Bohr Diagrams 1)Add the electrons. 2)Carbon has 6 electrons. 3)The first shell can only hold 2 electrons. C C

Bohr Diagrams 1)Since you have 2 electrons already drawn, you need to add 4 more. 2)These go in the 2 nd shell. 3)Add one at a time - starting on the right side and going counter clock-wise. C C

Bohr Diagrams 1)Check your work. 2)You should have 6 total electrons for Carbon. 3)Only two electrons can fit in the 1 st shell. 4)The 2 nd shell can hold up to 8 electrons. 5)The 3 rd shell can hold 18, but the elements in the first few periods only use 8 electrons. C C

MOLECULES ARE 2 OR MORE ATOMS ATTACHED TOGETHER –THEY CAN BE THE SAME KIND (ELEMENTS) –THEY CAN BE DIFFERENT KINDS (COMPOUNDS) Examples: H 2 O, NaCl.

COMPOUNDS ARE MADE OF 2 OR MORE KINDS OF ATOMS BONDED TOGETHER FOR A COMPOUND TO FORM, A CHEMICAL CHANGE MUST TAKE PLACE (A REACTION) THE ELEMENTS THAT COMBINE MAKE A NEW SUBSTANCE WITH NEW PHYSICAL PROPERTIES COMPOUNDS CANNOT BE BROKEN DOWN PHYSICALLY. REQUIRES A CHEMICAL CHANGE MORE COMMON THAN ELEMENTS += NaCl TABLE SALT

COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ELEMENTS. COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA += NaCl TABLE SALT

Chemical Changes Through Chemical Reactions A chemical reaction – Process in which the physical and chemical properties of the original substance change as new substances with different properties are formed m1.html

Chemical Formula Definition – Short way to write a compound using symbols. Subscript – Small number that is written below the element. Coefficient – The large number in front of the symbols.

Counting Atoms in Compounds. In compounds you will see elements and in some compound you will see small numbers behind the elements, example H 2 O, that small number is called a subscript. If the element does not have a subscript behind it, the subscript is 1. - The subscript tells you how many of those atoms are in that compound.

If there is a parentheses in the compound then you multiply the subscript behind the parentheses by the subscript that is behind the element in that parentheses. Counting Atoms in Compounds Ba(OH) 2 – 1) In this compound there are three different elements (Barium Hydroxide) they are Barium (Ba), Oxygen (O) and Hydorgen (H). 2) In this compound the subscript 2 goes with the 4. Oxygen is in the parentheses and the two elements in the paraentheses so there parentheses are Oxygen (O) and Hydrogen (H). is 2. Same for Hydrogen. 3) Since Ba is not in the parentheses and it does not have a subscript there is one Ba.

Why do elements bond? Elements bond to fill their outer shells. This make the element stable. Elements will either gain, lose or share electrons to fill their outer shell.

Three types of Chemical Bonds Chemically combining of two or more atoms 1. Covalent Bonds 2.Ionic Bonds 3.Hydrogen bonds These are not all the bonds but all we are going to cover.

In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. FK Ionic Bonds

Ionic bonding Ionic bonding involves 3 steps (3 energies) 1) loss of an electron(s) by one element, 2) gain of electron(s) by a second element, 3) attraction between positive and negative + Na e–e– Na + Ionization energy Cl e–e– + Cl – Electron affinity Lattice energy + Cl – Na + Cl – Na +

Covalent Bonds One or more pairs of electrons are shared by two atoms

Covalent Ionic CompoundsCompounds –Crystalline solids –High melting and boiling points –Conduct electricity when melted –Many soluble in water but not in nonpolar liquid –Gases, liquids, or solids –Low melting and boiling points –Poor electrical conductors –Many soluble in nonpolar liquids but not in water

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Single Covalent Bonds A single covalent bond is one in which two atoms share a pair of electrons. Structural formulas are chemical formulas that show the arrangement of atoms in molecules and polyatomic ions. –Chemical Formula Structural Formula H 2 H-H H 2 O NH 3 CH 4