NOTE: This presentation was not made for public use. Please do not use this presentations without my permission and the permission of each of the authors of the photographs, quotes, and other materials that they contain. Thank you, Vicki Hughes

Chemistry is all about elements. Elements are natural substances that cannot be broken down into simpler substances. Element or Not? X

Alchemy = Chemistry Gold was the most fascinating element during the middle ages.

All elements are composed of matter. All atoms of the same element have the same mass, and atoms of different elements have different masses. Compounds contain atoms of more than one element. In a particular compound, atoms of different elements always combine in the same way. All elements are composed of matter. All atoms of the same element have the same mass, and atoms of different elements have different masses. Compounds contain atoms of more than one element. In a particular compound, atoms of different elements always combine in the same way. All matter is made up of individual particles called atoms, which cannot be divided. John Dalton

Matter is anything that has mass and occupies space. All matter is made of atoms. Atoms are the smallest form of elements. About 100 elements Hydrogen is an element that accounts for about 90% of total mass of the universe. Hydrogen makes up about 1% of Earth’s crust and most of that is in water.

All of an atom’s positive charge is concentrated in the nucleus. Ernest Rutherford

Structure of an Atom Proton = positive charge Neutron = no charge The number of protons and neutrons varies with each element, however they are usually equal to each other. Electron = negative charge Protons and neutrons are grouped together in the nucleus. (Atomic Mass) e- Electrons move around the nucleus e-

Atomic Number = Number of protons The number of protons identifies an atom. Hydrogen atom

Atomic Mass Numbers = protons + neutrons # of Neutrons = Mass Number – Atomic Number Atomic Mass = 12 # of Neutrons 12 – 6 = 6

Dimitri Mendeleev I have created a periodic table where the elements are arranged according to their mass. This puts elements with similar properties in the same column. Yes, clearly I am a genius! ch?v=- wu0LixSBpk&list=UUZYTClx2T 1of7BRZ86-8fow

The periodic table organizes the atoms of the elements by properties and atomic number. Atomic Numbers PERIODIC TABLE OF THE ELEMENTS

Color of the elements symbol indicates the physical state of the element. Background color indicates whether the element is a metal, nonmetal, or metalloid. METALS METALOIDS NONMETALS

Properties of Matter Physical Properties Conductivity = ease with which electrons move through the material. Magnetism = ability to be attracted or repelled by another materials due to a magnetic field. Malleability = ability to be hammered or rolled into sheets. Solubility = measure of the ability to dissolve in another substance Density = amount of mass contained in a unit volume.

Properties of Matter Chemical Properties Reactivity = ability of a material to combine with or change into another substance.

Group – elements in a column with similar chemical and physical properties. Period – horizontal rows. Shows progression of the chemical properties of the elements. GROUP PERIOD

GROUP PERIOD Elements on the left of a period have a lower atomic mass than elements on the right of a period. Elements at the bottom of a group have more protons than elements at the top of the group.

Each element has a box that provide information about that element. C Atomic # Atomic Mass

How do you calculate the number of neutrons? Neutrons = Atomic Mass – Atomic Number C Atomic # Atomic Mass

Bohr-Rutherford Diagrams Bohr-Rutherford diagrams are a special type of illustration that shows the arrangement of ALL electrons around an atomic nucleus. Octet Rule states that no more than 8 electrons will be assigned to any shell.

Bohr-Rutherford Diagrams 1.Draw the nucleus as a circle.

Put the number of protons (atomic number) and neutrons (mass number - # of protons) in the nucleus. P=19 N=20 39 – 19 = 20

The electrons are in shells (levels) around the nucleus. 1st Shell = 2 electrons3rd Shell = 18 electrons 2nd Shell = 8 electrons4th shell = 32 electrons P=19 N=20

Draw the electrons by adding shells (circles) around the nucleus. The first shell has only 2 electrons. But the remaining shells usually have no more than 8 electrons. P=19 N=20 e- e-

ELECTRON CONFIGURATION Electrons in first 3 levels Valence Electrons are electrons in outermost shell.

Lewis Structures How many valence electrons does Nitrogen have? N

Lewis Structures Show the valence electrons in an atom – just the outmost level H O H O H H

Atoms are NEUTRAL if they have all of their electrons. Carbon is neutral if it has 6 electrons. C Atomic # Atomic Mass

Noble gases are those elements in group 8 that have perfectly filled electron shells. They therefore are least likely to combine with other elements

If an atom’s outermost level is mostly full, it is more likely to gain electrons and become more negative. If it has only 2 or 3 electrons in its outermost level it is more likely to lose electrons and become more positive. (except He – it is full with just 2 electrons). NaCl Who will lose and who will gain an electron? +

Because an atom has an equal number of protons and electrons, Atoms have no overall electrical charge. Atoms can gain or lose electrons and this forms an ion. x Lost 1 e- Became positive _ + Gained 1 e- Became negative

Molecular hydrogen (H 2 ), molecular oxygen (O 2 ) and molecular nitrogen (N 2 ) are not compounds because each is composed of a single element. A molecule is formed when two or more atoms join together chemically. If a molecule contains at least two different elements it is called a compound. H-H O=O : : :: : : N=N : : =

If a molecule contains at least two different elements it is called a compound. Water (H 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ) are compounds because each is made from more than one element. O H H O=C=O : : : :

ISOTOPES: variations of an element Have a different number of neutrons but same number of Protons Designated by the name of the element and its atomic mass number. Normal carbon nucleus 12 14

Any Questions?