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Chapter 6.1 Why do atoms combine_ - schoolnotes.com

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Chapter 6 Vocabulary
Section One: Why do atoms combine?1. Electron cloud-Area where negatively charged electrons, arranged in energy levels, travel around nucleus2. Energy level-The different positions for an electron in an atom3. Electron dot diagram-Chemical symbol for an element surrounded by as many dots as there are electrons in its outer energy level4. Chemical bond-Force that holds two atoms togetherSection Two: How Elements Bond1. Ion-atom that is positively or negatively charged because it has lost or gained electrons2. Ionic bond-attraction that holds oppositely charged ions close together3. Compound-substance produced when elements combine and whose properties are different from each of the elements4. Metallic bond-bond formed when metal atoms share their pooled electrons5. Covalent bond-chemical bond formed when atoms share electrons6. Molecule-natural particle formed when atoms share electronsPolar bond-bond in which electrons are shared unevenlyChemical formula-combination of chemical symbols and numbers that indicate which elements and how many atoms of each are present in a molecule
Chapter 6.1Why do atoms combine?
Atomic StructureNucleus: center of every atomMost of an atom’s mass is in the nucleusRest of atom is empty space except for the electronsElectrons are very small compared to the nucleusElectronsExact location of any one electron cannot be determinedElectron cloud: area of space around the nucleus where electrons are found.Compare/Contrast electrons around the nucleus of an atom to planets circling the Sun.
Chapter 6.1Why do atoms combine?
Element StructureEach element has a unique atomic structure with a specific number of protons, neutrons and electrons.# of protons = # of electrons in a neutral atomElectron ArrangementElectrons are responsible for many of an element’s physical and chemical properties.Electron energyEnergy levels: different areas for an electron in an atomEach level represents a different amount of energy
Chapter 6.1Why do atoms combine?
Number of ElectronsEach energy level can hold a maximum number of electrons.Energy Level 1 : one or two electronsEnergy Level 2: up to eight electronsEnergy Level 3: up to eighteen electronsEnergy Level 4: up to 32 electronsThe farther from the nucleus an energy level is, the more electrons it can hold
energy level models
Chapter 6.1Why do atoms combine?
Energy StepsElectrons in level closest to nucleus have the least amount of energy (pg.164)Use the formula 2n2wherenequals the number of the energy level, to determine the maximum number of electrons that can occupy that energy level.Ex: To determine the maximum number of electrons that can occupy level 3: 2(32) = 18The closer a negatively charged electron is to the positively charged nucleus, the more strongly it is attracted to the nucleusRemoving electrons close to the nucleus takes more energy than removing those that are farther away
energy level models
Chapter 6.1Why do atoms combine?
Electron ConfigurationThe number of electrons increases by one from left to right across a period(see periodic table; Hydrogen has 1, Helium has 2)Energy level one can hold a maximum of two electrons. Helium has 2 electrons in energy level one so it is complete and therefore stable.Each period in the periodic table ends with a stable element.
Chapter 6.1Why do atoms combine?
Element FamiliesEach column of the periodic table contains one element familyThe first element family starts with lithium and sodium in the first column (Hydrogen is considered separately)Members of element families have similar chemical properties because they have the same number of electrons in theirouter energy levels.Noble GasesNoble GasHalogensHALOGENSAlkali Metals
Element Families
NobleGases:Used to be known asinert gasesand thought to be totally unreactive.Name changed to Noble Gases when found that some of them can react.The most stable element familyNeon and the elements below it in Group 18 have 8 electrons in their outer energy levels.The energy levels are stable:they do not combine easily with other elements.Helium with 2 electrons in its energy level is also stable.Noble Gas
Element Families
HalogensThe elements in group 17 are called halogensMembers of the halogen family need one electron to obtain a stable outer energy level.The easier it is for a halogen to gain this electron to form a bond.Flourineis the most reactive of all halogens because its outer energy level is closest to the nucleus.The reactivity of the halogens decreases down the group as the outer energy levels get farther from the nucleus.HALOGENS
Element Families
Alkali MetalsGroup 1: alkali metalsEach have one outer energy level electronThe easier it is to remove an electron, the more reactive an atom isAlkali Metals1alkali metals 2fuse school alkali metalsLess energy is needed to remove an electron from an energy level that is farther from the nucleus than to remove one from an energy level that is closer to the nucleusApplying Science (pg. 167)
Chapter 6.1Why do atoms combine?
Electron Dot-Lewis Dot Diagrams
Electron Dot DiagramSymbol for the element surrounded by as many dots as there are electrons in its outer energy level.Only the outer energy level electrons are shown because these ae what determine how an element can react.How to draw a dot diagramElectron dot diagrams are used to show how atoms bond with each other. A chemical bond is the force that holds two atoms together.Atoms bond with other atoms in such a way that each atom becomes more stable
Chapter 6.1
Using Dot DiagramsUse electron dot diagrams to show how atoms bond with each otherAchemical bondis the force that holds two atoms together.Atoms bond with other atoms in a way that each atom becomes more stable8S: #1-4 on pg. 1698H: #1-5 on pg. 169
6.2 How Elements Bond
Ionic Bonds- Loss and Gain (pg. 170)Atoms form bonds with other atoms using the electrons in their outer energy levels. They have four ways to do this:losing electronsgaining electronspooling electronsSharing electrons
6.2 How Elements Bond
Ions- A Question ofBalance (pg. 171)An atom that is no longer neutral because it has lost or gained an electron is called an ion.Ions form when elements lose or gain electrons.Bond formation-Ionic bonds- attraction that holds oppositely charged ions close togetherCompound-a pure substance containing two or more elements that are chemically bonded.ionic bonds
6.2 How Elements Bond
Metallic Bonding-Pooling (pg. 172)Metallic bonds form when metal atoms share their pooled electrons.In a metal, the electrons in outer energy levels are not held tightly to individual atoms.The electrons move freely along all the ions in the metal forming a shared pool of electrons.
6.2 How Elements Bond
Metallic Bonding-Pooling (pg. 172)Metallic bonds form when metal atoms share their pooled electrons.This bonding affects the properties of metalsFor example, when metal is hammered into sheets or drawn into a wire, it does not break. Instead, the atoms slide over one another.Metallic bonding and conducting electricityOuter electrons in metal atoms readily move from one atom to the next to transmit current.Fuse School: Metallic Bonding
6.2 How Elements Bond
Covalent Bonds-Sharing (pg. 173)The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond.Shared electrons move back and forth between the outer energy levels of each atom in the covalent bond.Each atom has a stable outer energy level some of the time.Covalently bonded compounds are called molecular compounds
6.2 How Elements Bond
Covalent Bonds-Sharing (pg. 173)The neutral particle formed when atoms share electrons is called a molecule.A molecule is the basic unit of a molecular compoundNo ions are involved because no electrons are gained or lostCovalent bonding is another way that atoms become more stable. Sharing electrons allows each atom to have a stable outer energy level.crash course atomic bonding
6.2 How Elements Bond
Double and Triple Bonds(pg. 174)Sometimes an atom shares more than one electron with another atom. (see carbon dioxide example pg. 174)When two pairs of electrons are involved, it is a double bondWhen three pairs of electrons are shared by two atoms the bond is called a triple bond.
6.2 How Elements Bond
Polar and Nonpolar Molecules (pg. 174-175)Polar bond- a bond in which electrons are shared unevenly.This unequal sharing makes one side of the bond more negative than the other.When two pairs of electrons are involved, it is a double bondWhen three pairs of electrons are shared by two atoms the bond is called a triple bond.crash course polar and nonpolar
6.2 How Elements Bond
Polar and Nonpolar Molecules (pg. 174-175)Polar water molecule:.The oxygen atom has a greater share of the electrons in each bond.The oxygen end of water molecule has a slight negative charge and the hydrogen atom end has a slight positive charge.See balloon attraction on pg. 175.Nonpolar molecules: do not have uneven chargescrash course polar and nonpolar
6.2 How Elements Bond
Chemical Shorthand (pg.177)Alchemists used symbols to represent some elements(see pg. 177)Symbols for AtomsEach element is represented by a one-letter, two-letter, or three-letter symbolSome are the first letter of element name (ex: H for Hydrogen)Some are the first letter of element’s name in another language (ex: K for potassium, which stands forkalium, the Latin word for potassium)
6.2 How Elements Bond
Chemical Shorthand (pg.177-178)Symbols for CompoundsCompounds can be described using element symbols and numbers.Ex: When two hydrogen atoms form covalent bond, the resulting hydrogen molecule is written as H2.The subscript 2 tells us there are two hydrogen atoms in the molecule.Chemical Formula:a combination of chemical symbols and numbers that show which elements are present in a compound and how many atoms of each element are present.Note: When no subscript is present, the number of atoms is understood to be one.
Section 2 Review
a) Does lithium form a positive or negative ion? b) Doesflourineform a positive or negative ion? c) Write formula for the compound formed from these two elements:Explain the difference between polar and nonpolar bonds.Explain how a chemical formula indicates the ratio of elements in a compound.
Lithiumforms a positive ion Li+Flourineforms a negative ion F-LiF
2. In a nonpolar bond, electrons are shared equally; in a polar bond, they are unequal.
3. The subscripts tell the number of atoms in each element, so a ratio can be calculated

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Chapter 6.1 Why do atoms combine_ - schoolnotes.com