 # Atoms, Ions, and Molecules

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Atoms, Ions, and Molecules

Think about it… What do a frog, a skyscraper, a car, and your body all have in common?

ATOMS! Every physical thing you can think of, living or not, is made of incredibly small particles called atoms.

The atom The small basic unit of _____________. How small is an atom??
Matter – anything that takes up space and has mass How 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.

Atoms consist of three types of smaller particles:
Protons (+) Neutrons (neutral) Electrons (-) Notice the location of protons, neutrons, and electrons in an atom

Element Element – type of atom that can’t be broken down into a simpler substance Examples of elements: Hydrogen Lithium Carbon Boron

How do we identify an element?
Answer = by the number of protons Think about it: if Krypton loses a proton, is it still Krypton?? Atomic Number = number of protons

How can we identify the number of:
Protons = ____________ Neutrons = ___________ Electrons = ___________ From this picture?

THEN complete the formula below:
Atomic Number = number of protons **Number of protons and electrons is the same Atomic Weight To 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) (??)

Elements What four elements make up 96% of a human’s body mass?? 1.) 2.) 3.) 4.)

Elements What four elements make up 96% of a human’s body mass?? 1.) Carbon 2.) Oxygen 3.) Nitrogen 4.) Hydrogen

Review Where are protons and neutrons found in the atom?
Where are the electrons found in the atom?

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

The Bohr Model The first energy level can ONLY have up to 2 electrons
The remaining energy levels can have up to 8 Energy level

Practice Draw a Bohr model of an oxygen and calcium carbon atom.

Figure 2.3 Electron configurations-overview

Isotope – same number of protons (same element) different number of neutrons (different mass) Example: Carbon 12, Carbon 13, Carbon 14

Figure 2.2 Nuclei of the three naturally occurring isotopes of carbon-overview

When atoms gain or lose electrons
Ions – an atom that gained or lost one or more electrons is called an ion Why 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)

For example: Sodium (Na) has how many electrons? Chlorine (Cl) has how many electrons? Draw the Bohr model for each Who is closer to having a full outermost electron shell??

Na will give one of its electrons to chlorine
Becomes Na+ = positive charge = cation Cl will gain an electron from Na Becomes Cl- = negative charge = anion

Why are Ions important? Hydrogen ions (H+) are needed for the production of usable chemical energy in cells Calcium ions (Ca2+) are necessary for every muscle movement in your body Chloride ions (Cl-) are important for sending chemical signals to your brain

Ionic Bonds Forms through the electrical force between oppositely charged ions Think back to NaCl that we just talked about

Ionic Bond Have you ever heard positive and negative attract?
It’s the same here! Na+ attracts to Cl- NaCl = table salt The positive sodium ion (Na+) and negative chloride ion (Cl-) attract to each other and form an ionic bond

BUT, Not all atoms easily gain or lose electrons…
It is possible for atoms to share electrons A covalent bond forms when atoms share a pair of electrons Draw a Bohr model for oxygen and carbon How many electrons does oxygen need to fill its outermost shell? How many electrons does carbon need to fill its outermost shell?

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

Water (H2O) is a covalent bond

What is a molecule? Molecule- two or more atoms held together by covalent bonds For example: H2O, CO2, O2, etc. **Almost all of the substances that make up organisms are molecules held together by covalent bonds

Compounds A substance made of different elements bonded together in a certain ratio Held together by chemical bonds H2O, CO2, NaCl….can you think of any others?