Chapter 4- Earth Chemistry Section 1- Matter Section 2- Combinations of Atoms

Chapter 4- Earth ChemistrySection 1- Matter

Section 2- Combinations of Atoms

Section 1- Matter

• Objectives1. Compare chemical properties and physical properties of

matter

2. Describe the basic structure of an atom

3. Compare atomic number, mass number, and atomic mass

4. Define Isotope

5. Describe the arrangement of elements in the periodic table

Section 1- Matter

• Introduction• Every object in the universe is made of particles of some

kind of substance• Scientist use the word matter to describe the substances of

which objects are made• Matter is anything that takes up space and has a mass• The amount of matter in any object is the mass of that

object• All matter has observable and measurable properties

Section 1- Matter

• Properties of Matter• Physical Properties• Ex; density, color, hardness, freezing point, boiling point, and

the ability to conduct an electric current

• Chemical Properties• Ex; For Iron- Iron reacts with Oxygen to form rust

Section 1- Matter

• Properties of Matter (Elements)

• A substance that cannot be broken down into simpler, stable substances by chemical means

• Each element has a characteristic set of physical and chemical properties that can be used to identify it

Section 1- Matter

• Properties of Matter (Elements)• More than 90 elements occur naturally on Earth• About 2 dozen have been created in laboratories• Of the natural elements 8 make up more than 98% of the

Earth’s crust• Every known element is represented by a symbol of one or

two letters

Section 1- Matter

• Properties of Matter (Atoms)• Elements consist of atoms• An atom is the smallest unit of an element that has the

chemical properties of that element• Atoms cannot be broken down into smaller particles that

will have the same chemical and physical properties as the atom

• A single atom is so small its size is hard to imagine

Section 1- Matter

• Atomic Structure• Subatomic Particles• Protons (+)• Electrons (-)• Neutrons (no charge)

Section 1- Matter

• Atomic Structure (The Nucleus)• Protons and Neutrons of an atom are packed close to one

another• Together they form the nucleus, which is the small region in

the center of an atom• The nucleus has a positive charge• The nucleus makes up most of an atom’s mass, but very little

of the atom’s volume

Section 1- Matter

• Atomic Structure (The Electron Cloud)• The electrons of an atom move in a certain region of space

called an electron cloud that surround the nucleus• Because opposite charges attract each other, the negatively

charged electrons are attracted to the positively charged nucleus

• This attraction is what holds electron in the atom

Section 1- Matter

Section 1- Matter

• Atomic Number

• The number of protons in the nucleus of an atom

• All atoms of any given element have the same atomic number

• Elements on the periodic table are ordered according to their atomic number

Section 1- Matter

• Atomic Mass

• The sum of the number of protons and neutrons in an atom

• Atomic Mass Unit (amu)

• Protons and Neutrons each have an atomic mass that is close to 1 amu

Section 1- Matter

• Atomic Mass (Isotope)

• Same number of Protons

• Neutrons may differ

• An atom that has the same number of protons as other atoms of the same element do but has a different number of neutron is called an isotope

Section 1- Matter

• Atomic Mass ( Average Atomic Mass)• The average atomic mass is the weighted average of the

atomic masses of the naturally occurring isotopes of an element

Section 1- Matter

• Valence Electrons and Periodic Properties

• Based on similarities in their chemical properties, elements on the periodic table are arranged in columns, called groups

• An atom’s chemical properties are largely determined by the number of the outermost electrons in an atom’s electron cloud, these electrons are called valence electrons

Section 1- Matter

• Valence Electrons and Periodic Properties• Groups 1 &2• The number of valence electrons in each atom is the same as that

atom’s group number

• Groups 3-12• Have 2 or more valence electrons

• Groups 13-18• The number of valence electrons in each atom is the same as the

atom’s group number minus 10, EXCEPT for Helium

• Group 18• Have 8 valence electrons

Section 1- Matter

• Valence Electrons and Periodic Properties• Elements whose atoms have only 1,2, or 3 valence electrons

tend to lose electrons easily• These elements have metallic properties and are generally

classified as metals

• Elements whose atoms have from 4-7 valence electrons are more likely to gain electrons• Many of these elements, which are in Groups 13-17, are

classified as nonmetals

Section 1- Matter


• Objectives1. Define compound and molecule

2. Interpret chemical formulas

3. Describe two ways that electrons form chemical bonds between atoms

4. Explain the differences between compounds and mixtures


• Introduction

• A substance that is made of two or more elements that are joined by chemical bonds between atoms of those elements is called a compound

• The properties of a compound differ from those of the elements that make up the compound


• Molecules• The smallest unit of matter that can exist by itself and retain

all of a substance’s chemical properties• In a molecule of two or more atoms, the atoms are

chemically bonded together• Some molecules consist entirely of atoms of the same

element• Some elements occur naturally as diatomic molecules,

which are molecules that are made up of only two atoms


• Chemical Formulas• A combination of letters and numbers that shows which

elements make up a compound• Shows the number of atoms of each element that are

required to make a molecule of a compound• The chemical formula for water is H2O• This indicates that each water molecule consists of two atoms

of hydrogen and one atom of oxygen


• Chemical Equations

• Elements and compounds often combine through chemical reactions to form new compounds

• The reaction of these element and compound can be described in a formula called a chemical equation


• Chemical Equations (Equation Structure)

• Reactants are on the left-hand side of the arrow, form the products, which are on the right-hand side of the arrow

• When chemical equations are written the arrow means “gives” or “yields”

CH4 + 2O2 CO2 + 2 H2O


• Chemical Equations (Balanced Equations)

• A chemical equation is balanced when the number of atoms of each element on the right side of the equation is equal to the number of atoms of the same element on the left side

• To balance an equation, you must put numbers called coefficients in front of the chemical formula


• Chemical Bonds

• The forces that hold together the atoms in the molecules

• They are formed because of the attraction between positive and negative charges

• Atoms form chemical bonds by either sharing or transferring valence electrons from one atom to another


• Chemical Bonds (Ions)

• An atom or molecule that has gained or lost one or more electrons and has a negative or positive charge


• Chemical Bonds (Ionic Bonds)

• The attractive force between oppositely charged ions, which form when electrons are transferred from one atom or molecule to another

• Most ionic compounds form when electrons are transferred between the atoms of metallic and nonmetallic elements


• Chemical Bonds (Covalent Bonds)

• A bond formed when atoms share one or more pairs of electrons

• When atoms share electrons , the positive nucleus of each atom is attracted to the shared negative electrons.


• Chemical Bonds (Polar Covalent Bonds)

• A covalent bond in which the bonded atoms have an unequal attraction for the shared electrons


• Mixtures

• A combination of two or more substances that are not chemical combined

• Substances that make up a mixture keep their individual properties

• Unlike compounds, a mixture can be separated into its parts by physical means


• Mixtures (Heterogeneous Mixtures)

• Mixtures in which two or more substances are not uniformly distributed


• Mixtures (Homogeneous Mixtures)

• A homogeneous mixture of two or more substances that are uniformly dispersed throughout the mixture is a solution

Chapter 4- Earth Chemistry

•Questions

?’s

Documents

Chapter 4- Earth Chemistry Section 1- Matter Section 2- Combinations of Atoms