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2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions.

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Presentation on theme: "2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions."— Presentation transcript:

1 2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions.

2 2.1 Atoms, Ions, and Molecules Contains: a. nucleus has protons and neutrons. b. electrons are in energy levels – regions around the nucleus. Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) An atom –smallest basic unit of matter

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6 Elements Matter that has atoms that are all alike are elements. Elements cannot be broken down into smaller substances. Elements are listed on the Periodic Table. More than 90% of the human body is made of only carbon, hydrogen, oxygen, and nitrogen.

7 2.1 Atoms, Ions, and Molecules Most abundant elements The most common elements found in living things are Carbon, Hydrogen, Nitrogen, and Oxygen. Oxygen, at 65%, is the element that makes up most mass in the human body. Carbon follows with 18.5%, then hydrogen with 9.5%, and then nitrogen with 3.3%.

8 2.1 Atoms, Ions, and Molecules Living things consist of atoms of different elements. An atom is the smallest basic unit of matter. An element is one type of atom. H O Hydrogen atom (H) Oxygen atom (O)

9 2.1 Atoms, Ions, and Molecules –water (H 2 O) O HH _ ++ A compound is made of atoms of different elements bonded together.

10 2.1 Atoms, Ions, and Molecules –carbon dioxide (CO 2 ) –Glucose A compound is made of atoms of different elements bonded together. –water (H 2 O)

11 2.1 Atoms, Ions, and Molecules An ion forms when an atom gains or loses one or more electrons. –positive ions -formed when atoms lose electrons –negative ions -formed when atoms gain electrons Ionic bonds –chemical force due to electircal attraction between oppositely charged ions. Sodium atom (Na)Chlorine atom (CI)Sodium ion (Na + )Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron

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13 Covalent bonds form when atoms SHARE electrons in their outer energy level. This allows both atoms to become full and stable. covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 ) Molecules- atoms bonded together by covalent bonds

14 2.1 Atoms, Ions, and Molecules Covalent bonds Most organic (coming from living things) compounds have covalent bonds. This includes sugars, fats, proteins, and water.

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17 Compounds you need to know: H 2 O = water CO 2 = carbon dioxide C 6 H 12 O 6 = sugar (usually glucose) NaCl = table salt NH 3 = ammonia

18 2.1 Atoms, Ions, and Molecules Isotopes Atoms with the same number of protons and electrons but different numbers of neutrons are called isotopes. Isotopes have the same element, but may have different properties because of their different masses that may change its stability. Isotopes are named by adding the number of protons and neutrons. Some isotopes are useful in telling the age of fossils.


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