ATOMS AND THE PERIODIC TABLE chapter three

ATOMIC THEORY - history 4 TH CENTURY B.C. Matter is made of tiny particles called ATOMS. John DALTON ELEMENTS are made of particles called atoms. ATOMS of the same elements are alike. ATOMS form molecules. EARLY 1900’s (1913) ELECTRONS orbit like planets in the solar system. MID 1900’s (after 1925) Modern theory 3.1 Atomic Structure

ATOMIC THEORY - STRUCTURE MODEL OF THE ATOM ELECTRON - NUCLEUS PROTON + NEUTRON (NEUTRAL) ENERGY LEVELS 3.1 Atomic Structure

ATOMIC STRUCTURE ELECTRON LOCATION Electrons are found in energy levels of an atom. Electrons occupy the lowest energy level available. 3.1 Atomic Structure

Energy Levels are like ladder rungs… GAINING ENERGY 3.1 Atomic Structure

Energy Levels 3.1 Atomic Structure

ORBITALS – where the electrons are located within an energy level. S orbital (Like a sphere) may contain up to 2 electrons first energy level is an s orbital 3.1 Atomic Structure

P orbital (Like a dumbbell) may contain up to 2 electrons second energy level may contain an s orbital and up to 3 p orbitals 3.1 Atomic Structure

Orbitals 3.1 Atomic Structure

Valence electrons are located in the outermost energy level of an atom. They determine the chemical properties of an element. 3.1 Atomic Structure

3.2 A TOUR OF THE PERIODIC TABLE Properties of elements change in a regular pattern that the table helps to describe. Periods – Horizontal Rows Groups(families) – Vertical Columns

Traditional Periodic Table Los Alamos National Laboratory's Chemistry Division Presents a Periodic Table of the Elements 3.2 Guided Tour of Periodic Table

The number of protons in an atom determines an element’s location on the table. 3.2 Guided Tour of Periodic Table

6 C Carbon ATOMIC NUMBER SYMBOL NAME MASS PROTONS (and ELECTRONS too) PROTONS + NEUTRONS MASS # Elements On the Periodic Table 3.2 Guided Tour of Periodic Table

PROTONS AND NEUTRONS HAVE EQUAL MASS. ELECTRONS ARE TINY – 1800 EQUAL ONE PROTON. 3.2 Guided Tour of Periodic Table

MASS 35 ATOMIC NUMBER 17 Cl protons _?_electrons _?_ neutrons _?_ 3.2 Guided Tour of Periodic Table

MASS 35 ATOMIC NUMBER 17 Cl protons 17electrons 17 neutrons = Guided Tour of Periodic Table

IONS are atoms that have lost or gained an electron. ELECTRON GAINED = NEGATIVE CHARGE (-) ELECTRON LOST = POSITIVE CHARGE (+) 3.2 Guided Tour of Periodic Table

Na+ Cl Electron transfer 3.2 Guided Tour of Periodic Table

TWO KINDS OF IONS: A (+) CHARGED ION IS A Cation. A (-) CHARGED ION IS AN Anion. EXAMPLES: LITHIUM FLUORIDE 3.2 Guided Tour of Periodic Table

The atoms of an element always have the same number of protons. BUT….. The atoms of an element may have different numbers of neutrons. This is an ISOTOPE! Two carbon ISOTOPES: CARBON 12 = 6 protons and 6 neutrons CARBON 14 = 6 protons and 8 neutrons 3.2 Guided Tour of Periodic Table

The AVERAGE MASS of an ATOM Why is the mass number not an even number? –Atoms of the same element exist with different numbers of neutrons. –This makes the mass of different atoms of the same element different. –The average mass is a weighted number so that more common isotopes have a greater affect on the average than rare isotopes. What is an amu? –It is an “atomic mass unit”. –An amu is equivalent to the mass of 1/12 of a carbon-12 atom. 3.2 Guided Tour of Periodic Table

3.3 FAMILIES OF ELEMENTS: HAVE THE SAME VALENCE NUMBER. HAVE SIMILAR CHEMICAL AND PHYSICAL PROPERTIES. A COLUMN OF ELEMENTS IS A FAMILY.

TWO MAJOR DIVISIONS METALSNONMETALS 3.3 Families of Elements

GROUP ONE: ALKALI METALS VERY REACTIVE ONE VALENCE ELECTRON 3.3 Families of Elements

GROUP TWO: ALKALINE EARTH METALS TWO VALENCE ELECTRONS 3.3 Families of Elements

GROUP 3-12: TRANSITION METALS MANY COMMON METALS NOT AS REACTIVE AS OTHER METALS 3.3 Families of Elements

GROUP 17: HALOGENS VERY REACTIVE FORM SALTS WITH ALKALI METALS 7 VALANCE ELECTRONS 3.3 Families of Elements

GROUP 18: NOBLE GASES INERT / UNREACTIVE EIGHT VALENCE ELECTRONS 3.3 Families of Elements

SYNTHETIC ELEMENTS They are man-made and radioactive. They include all elements above #92, plus #43 and # Families of Elements

SEMICONDUCTORS (METALOIDS) The elements that are between the metals and nonmetals are known as: SEMICONDUCTORS (METALOIDS) They may exhibit metallic and nonmetallic properties. B Si GeAs 3.3 Families of Elements

3.4 USING MOLES TO COUNT ATOMS Some counting units: –Reams of paper –Dozens of eggs –Atomic mass units of protons and neutrons –Moles of atoms A mole is the SI unit that describes the amount of a substance. Avogadro’s constant is the number of particles in one mole which = x10 23 molar mass is the mass in grams of one mol of a substance…it is equal to the average atomic number of an atom.

Vocabulary Parts of an atom History Element families Using the periodic table Metal vs. nonmetal Chapter 3 Studying for the Test