Introduction to Chemistry Chapter 5 Section 5.1 Courtesy of Mrs. Wyckoff Click Here to Play the Element Song!

Chemistry is the Study of Matter Matter is a substance: that has mass and occupies space!

All matter has two properties: _______________ which is a measure of the amount of material in a substance, and _______________ which is the amount of space an object occupies. mass volume

Weight is a measure of the force of gravity.

All matter is composed of simple substances that cannot be broken down by ordinary chemical means called elements.

Elements are given symbols that contain one or two letters. If the symbol has just one letter, it is capitalized. For example: If the symbol has two letters, only the first is capitalized, the second is written in lower case. C He

An __________________ is the smallest part of an element that has all the properties of that element. atom

Elements may combine chemically to form _____________. compounds

A ___________ is the smallest part of a compound that has all the properties of that compound. molecule

A ___________ is a physical combination of two or more substances, each of which retains its individual properties. mixture

Compounds differ from mixtures in the following ways: CompoundsMixtures New Properties Substances Keep Original Properties Separated Chemically Separated Physically Proportions Fixed Proportions Vary

Atoms are composed of three types of particles: ParticleLocationChargeMassRelative Mass ProtonNucleus X g1 amu NeutronNucleus X g1 amu ElectronOutside Nucleus X g0 amu amu = atomic mass unit

Electrons can be found at any location away from the nucleus, but they are more likely to be in certain regions than in others. The regions in space in which it is likely to find electrons are known as energy levels or orbitals.

Each energy level is able to contain only a certain number of electrons. Electrons fill the energy levels closest to the nucleus first. When one energy level is filled, electrons must move to another energy level further away from the nucleus.

1s 2 2s 2 Nucleus 2p 6 When one energy level is filled, electrons must move to another energy level further away from the nucleus.

Second shell Helium 2 He First shell Third shell Hydrogen 1 H 2 He 4.00 Atomic Mass (#p+ #n) Atomic number (#p) Element symbol Electron-shell diagram Lithium 3 Li Beryllium 4 Be Boron 3 B Carbon 6 C Nitrogen 7 N Oxygen 8 O Fluorine 9 F Neon 10 Ne Sodium 11 Na Magnesium 12 Mg Aluminum 13 Al Silicon 14 Si Phosphorus 15 P Sulfur 16 S Chlorine 17 Cl Argon 18 Ar Electrons determine the chemical reactivity of an atom: Electron-shell diagrams of the first 18 elements Chemical reactivity depends mostly on the number of valence electrons (in outermost shell). Atoms are most stable when their outermost electron shell is filled with 8 electrons (or 2 for H and H).

Atoms tend to be most stable when their outer energy level contains eight electrons. Atoms gain, lose or share electrons in an attempt to obtain eight outer, or valence, electrons. Nucleus 1s 1 1s 2 Hydrogen Helium

Atoms tend to be most stable when their outer energy level contains eight electrons. Atoms gain, lose or share electrons in an attempt to obtain eight outer, or valence, electrons. Nucleus 2s 1 Lithium Beryllium 1s 2 2s 2

Atoms tend to be most stable when their outer energy level contains eight electrons. Atoms gain, lose or share electrons in an attempt to obtain eight outer, or valence, electrons. Nucleus 1s 2 2s 2 2p 1 Boron Carbon 2p 2

Atoms tend to be most stable when their outer energy level contains eight electrons. Atoms gain, lose or share electrons in an attempt to obtain eight outer, or valence, electrons. Nucleus 1s 2 2s 2 2p 3 Boron Nitrogen 2p 4 Oxygen

Atoms tend to be most stable when their outer energy level contains eight electrons. Atoms gain, lose or share electrons in an attempt to obtain eight outer, or valence, electrons. Nucleus 1s 2 2s 2 2p 5 Boron Fluorine 2p 6 Neon Click Here for animation of electron shell filling!

The number of protons in an element is indicated by the ______________, which is given the symbol Z. Z atomic number

In neutral atoms, the number of electrons is equal to the number of protons. ________________, which is given the symbol A, is equal to the number of protons plus the number of neutrons. Atomic mass A

The number of neutrons is thus the atomic mass minus the atomic number. Atomic Mass rounded to whole # Atomic Number - 27 # of Neutrons Atomic Mass = Atomic Mass Rounded Off

Example: Lithium Atomic mass Number of protons Number of electrons Number of neutrons Complete Symbol: 3 Atomic number 7 amu Li 7 3 atomic mass atomic number Remember! Atomic mass – Atomic number = # Neutrons

Isotopes Forms of an element that have the same number of protons, and electrons, but different numbers of neutrons and different masses are called ____________. isotopes For example: Hydrogen has three common isotopes H 1 1 Protium H 2 1 Deuterium H 3 1 Tritium - Which is Radioactive!

Three Isotopes of Hydrogen Characteristic HHH Atomic #111 Atomic Mass123 # protons111 # electrons111 # neutrons

Ions A charged particle is called a(n) _______. Ions are formed by the gain or the loss of __________. ion electrons

Positive Ions If an atom loses electrons, it has fewer negative charges than it has positive charges, and thus becomes a ___________ charged particle, known as a _______. Metals, found on the _____ side of the periodic table, tend to form positive ions. positively cation left

Positive Ions Left Side of Table

Negative Ions If an atom gains electrons, it has more negative charges than it has positive charges, and thus becomes a ___________ charged particle, known as a _______. Nonmetals, found on the _____ side of the periodic table, tend to form negative ions. negatively anions right

Negative Ions Right Side of Table

Example: Sodium (Na) Ion – Loses one electron Sodium AtomSodium Ion # of Protons # of electrons symbol Na 0 Na +1 Na + or Na 1+ or Na

Example: Sulfur (S) Ion – Gains two electron Sulfur AtomSulfur Ion # of Protons # of electrons symbol S0S0 S -2 S -- or S 2-

Chemical Bonding A chemical _______ is a force that holds atoms together in compounds. There are two major types of chemical bonds: bond

Chemical Bonding In _______ bonds, electrons are transferred from a metal, which loses electrons, to a nonmetal, which gains electrons. The resulting ions have opposite electrical charges, and are strongly attracted to one another. ionic

Example of Ionic Bonding F Li LiF

Example of Ionic Bonding F -1 Li +1 lost 1 electron gained 1 electron now 10 electrons now 2 electrons LiF

Chemical Bonding In _________ bonds, two nonmetals share electrons. covalent Non-Metals

Examples of Covalent Bonding H F H HF

Ionic and Covalent Bond Movie