Matter Chapter 2, Section 1. Elements and the Periodic Table Element – a substance that cannot be...
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Transcript of Matter Chapter 2, Section 1. Elements and the Periodic Table Element – a substance that cannot be...
MatterMatter
Chapter 2, Section 1Chapter 2, Section 1
Elements and the Periodic TableElements and the Periodic Table Element – a substance that cannot be broken
down into simpler substances by ordinary chemical or physical means
There are more than 112 known elements, and new elements continued to be discovered
92 elements occur naturally, the others are produced in laboratories
The rows in the periodic table are called periods, and the columns are called groups
Of the known elements, only eight make up most of Earth’s continental crust (Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, and Magnesium); six of which are metals
Concept CheckConcept Check
What is an element?A class of matter that contains only one
type of atom; an element cannot be broken down, chemically or physically, into a simpler substance with the same properties.
AtomsAtoms An atom is the smallest particle of matter that contains
the characteristics of an element The central region of an atom is called the nucleus;
the nucleus contains positive charged protons and neutrons, which have no electrical charge; negatively charged electrons orbit the nucleus
Protons and neutrons have the same mass Atomic Number – the number of protons in the
nucleus of an atom Atoms have the same number of protons as electrons An electron is the smallest of the 3 fundamental
particles in an atom, with a mass of about 1/1836 the mass of a proton or neutron
Energy Level – one of several distinct regions around the nucleus of an atom where electrons are located
Two Models of an AtomTwo Models of an Atom
Concept CheckConcept CheckHow are electrons, protons, and neutrons
alike and how are they different?They are all subatomic particles that make
up atoms. Protons have positive electrical charges, neutrons have no charge, and electrons have negative charges. Protons and neutrons are found in an atom’s nucleus. Electrons move about the nucleus.
IsotopesIsotopes
Atoms of the same element always have the same number of protons, but the number of neutrons for atoms of the same element can vary
Isotope – an atom with the same number of protons but different numbers of neutrons for a given element; an isotope’s mass number is different from that of a given element
Mass Number – the number of protons and neutrons in the nucleus of an atom
The nuclei of most atoms are stable, but many elements have atoms whose nuclei are unstable; radioactive decay occurs when the forces that hold the nucleus together are not strong enough
Carbon IsotopesCarbon Isotopes
Concept CheckConcept Check
What are isotopes?Atoms of the same element with the same
number of protons but different numbers of neutrons.
Why Atoms BondWhy Atoms Bond Most elements exist combined with other elements to
form substances with properties that are different from the elements themselves
Compound – a substance formed by the chemical combination of two or more elements in definite proportions and usually having properties different from those of its constituent elements
Compounds form when atoms are more stable (exist at a lower energy state) in a combined form
The chemical process, called bonding, centers around the electron arrangement of atoms
When an atom’s outermost energy level does not contain the maximum number of electrons, the atom is more likely to form a chemical bond with one or more atoms
Chemical Bond – a force that holds together atoms that form a compound
Chemical Bonding of Sodium and Chemical Bonding of Sodium and ChlorideChloride
Concept CheckConcept Check
Why do compounds form?Compounds form as a result of changes in
the arrangement of electrons in the outermost shells of the bonded atoms.
Types of Chemical BondsTypes of Chemical Bonds An atom that gains electrons becomes negatively
charged, and an atom that loses electrons becomes positively charged, because the number of protons and electrons are no longer equal
Ion – an atom or a molecule that possesses an electric charge
Oppositely charged ions attract each other to form crystalline compounds
Ionic Bond – a bond that forms between negative and positive ions
Covalent Bond – a bond that forms when atoms share electrons
The smallest particle of a covalent compound that shows the properties of that compound is a molecule
Metallic Bond – a bond that forms when electrons are shared by metal ions
Ionic BondsIonic Bonds
Covalent Covalent BondsBonds
Metallic BondsMetallic Bonds
Concept CheckConcept Check
What happens when two or more atoms react?
Electrons are gained, lost or shared when two or more atoms react to form a compound.
AssignmentAssignment
Read Chapter 2, Section 1 (pg. 34-43)Read Chapter 2, Section 1 (pg. 34-43)Do Section 2.1 Assessment #1-10 (pg. 43)Do Section 2.1 Assessment #1-10 (pg. 43)