2 Think about it…What do a frog, a skyscraper, a car, and your body all have in common?
3 ATOMS!Every physical thing you can think of, living or not, is made of incredibly small particles called atoms.
4 The atom The small basic unit of _____________. How small is an atom?? Matter – anything that takesup space and has massHow small is an atom??Millions and millions of atoms could fit in the space the size of the period at the end of this sentence.
5 Atoms consist of three types of smaller particles: Protons (+)Neutrons (neutral)Electrons (-)Notice the locationof protons, neutrons,and electrons in an atom
6 ElementElement – type of atom that can’t be broken down into a simpler substanceExamples of elements:HydrogenLithiumCarbonBoron
7 How do we identify an element? Answer = by the number of protonsThink about it: if Krypton loses a proton, is it still Krypton??Atomic Number = number of protons
8 How can we identify the number of: Protons = ____________Neutrons = ___________Electrons = ___________From this picture?
9 THEN complete the formula below: Atomic Number = number of protons**Number of protons and electrons is the sameAtomic WeightTo find the number of neutrons you have to find the mass number. To find the mass number, all you need to do is round the atomic weight to the nearest whole number. In our example, krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84.THEN complete the formula below:Mass Number = (Number of Protons) + (Number of Neutrons)84 = (36) (??)
10 ElementsWhat four elements make up 96% of a human’s body mass?? 1.) 2.) 3.) 4.)
11 ElementsWhat four elements make up 96% of a human’s body mass?? 1.) Carbon 2.) Oxygen 3.) Nitrogen 4.) Hydrogen
12 Review Where are protons and neutrons found in the atom? Where are the electrons found in the atom?
13 The Bohr Model Niels Bohr introduced “The Bohr Model” in 1913 Model that shows the atoms electrons located outside the nucleus in regions called energy levels (valence shell)Energy levels
14 The Bohr Model The first energy level can ONLY have up to 2 electrons The remaining energy levels can have up to 8Energy level
15 PracticeDraw a Bohr model of an oxygen and calcium carbon atom.
17 Isotope – same number of protons (same element) different number of neutrons (different mass) Example: Carbon 12, Carbon 13, Carbon 14
18 Figure 2.2 Nuclei of the three naturally occurring isotopes of carbon-overview
19 When atoms gain or lose electrons Ions – an atom that gained or lost one or more electrons is called an ionWhy do atoms gain or lose electrons?Atoms want a full outermost energy level (valence shell)When an atom loses or gains electrons it has an electrical charge (positive or negative)
20 For example:Sodium (Na) has how many electrons?Chlorine (Cl) has how many electrons?Draw the Bohr model for eachWho is closer to having a full outermost electron shell??
21 Na will give one of its electrons to chlorine Becomes Na+ = positive charge = cationCl will gain an electron from NaBecomes Cl- = negative charge = anion
22 Why are Ions important?Hydrogen ions (H+) are needed for the production of usable chemical energy in cellsCalcium ions (Ca2+) are necessary for every muscle movement in your bodyChloride ions (Cl-) are important for sending chemical signals to your brain
23 Ionic BondsForms through the electrical force between oppositely charged ionsThink back to NaCl that we just talked about
24 Ionic Bond Have you ever heard positive and negative attract? It’s the same here!Na+ attracts to Cl-NaCl = table saltThe positive sodium ion (Na+) and negative chloride ion (Cl-) attract to each other and form an ionic bond
25 BUT, Not all atoms easily gain or lose electrons… It is possible for atoms to share electronsA covalent bond forms when atoms share a pair of electronsDraw a Bohr model for oxygen and carbonHow many electrons does oxygen need to fill its outermost shell?How many electrons does carbon need to fill its outermost shell?
26 Carbon dioxide (CO2) is a covalent bond An oxygen atom needs two electrons to fill its outer energy level. A carbon atom needs 4 electrons to fill its outer energy level. In carbon dioxide, carbon makes a double bond, or SHARES two pairs of electrons with each oxygen atom
28 What is a molecule?Molecule- two or more atoms held together by covalent bondsFor example: H2O, CO2, O2, etc.**Almost all of the substances that make up organisms are molecules held together by covalent bonds
29 CompoundsA substance made of different elements bonded together in a certain ratioHeld together by chemical bondsH2O, CO2, NaCl….can you think of any others?