Mr. Perez

 On the periodic table of elements, the number above the element’s abbreviation (atomic number) counts the number of _________ the element contains.  Electrons  Protons  Neutrons  Doughnuts

 Carbon, hydrogen, oxygen and ____________ make up 96% of living matter.  Helium  Nitrogen  Boron  Potassium

 ____________ bonds are formed when two atoms share a pair of valence electrons.  Ionic  Hydrogen  Covalent  Double

 TRUE or FALSE  If an element has 10 electrons, its electron distribution will have 2 electrons in the first valence shell and 8 in the second valence shell.

 Organisms are composed of matter, or anything that takes up space and has mass  Matter is made up of elements, substances that cannot be broken down to other substances by chemical reactions

 Compounds are made up of two or more elements and have characteristics different from the elements that make it up Sodium (Na) + Chlorine (Cl) = Table Salt (NaCl)

 Carbon, Hydrogen, Oxygen, and Nitrogen make up 96% of living matter  REMEMBER: CHON = LIFE  The other 4% of living matter is made up of trace elements such as potassium, calcium, phosphorous and sulfur.

 T he structure of atoms that makes up an element allows it to have certain properties  Atoms are the smallest units of matter that still retain the properties of an element  Atoms are made up of:  Protons (+) = atomic mass  Neutrons (0)  Electrons (-)

 An element’s energy level depends on the distribution of valence electrons  Valence electrons are the electrons found in the outermost shell  Full shells are less reactive than those that are empty or missing a few electrons

First shell Second shell Third shell Hydrogen 1 H Lithium 3 Li Sodium 11 Na Beryllium 4 Be Magnesium 12 Mg Boron 5 B Aluminum 13 Al Carbon 6 C Silicon 14 Si Nitrogen 7 N Phosphorus 15 P Oxygen 8 O Sulfur 16 S Fluorine 9 F Chlorine 17 Cl Neon 10 Ne Argon 18 Ar Helium 2 He 2 He 4.00 Mass number Atomic number Element symbol Electron distribution diagram

 Atoms with incomplete valence shells can share or transfer electrons with other atoms  Chemical bonds keep them together  Covalent bonds involve the sharing of electrons  Single bonds is the sharing of one pair of electrons  Double bonds is the sharing of two pairs of electrons  Ionic bonds involve the loss or gain of an electron  Cation= + charged ion  Anion = - charged ion

 Molecules are formed by two or more atoms held together by covalent bonds  We use structural formulas to represent atoms that are bonded together  For example H—H, which can also be written H 2  Compounds are formed when two or more different elements combine

(a) Hydrogen (H 2 ) (b) Oxygen (O 2 ) (c) Water (H 2 O) Name and Molecular Formula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (d) Methane (CH 4 )

 STRONG = COVALENT  WEAK = IONIC & HYDROGEN  These weak bonds help retain shapes

 Hydrogen bonds are formed when a hydrogen atom is covalently bonded to an electronegative atom and is attracted to another electronegative atoms  Usually, the electronegative partners are oxygen or nitrogen  Electronegativity is an atom’s attraction for electrons in a covalent bond  The stronger the electronegativity the more electrons will be pulled to itself when sharing

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