Introductory Chemistry Mrs. Taktak

Atoms Most of the Universe consists of matter and energy.matter All matter is composed of basic elements –In your own words, define these terms. What is an atom??? –The smallest unit of matter that has all the properties of a given element. Ex.) Gold is made up of Gold atoms!

What does an Atom look like? In the center is a Nucleus In the nucleus are 2 smaller particles called: Protons and Neutrons –Protons have a (+) charge and Neutrons have (0) charge. Each element has a different number of protons in the nucleus.

What does an Atom look like? Outside of the nucleus are rings called shells. Floating around the shells are Electrons –What charge do you think an electron has?? –Based on what you know, diagram what you think an atom looks like. Label the parts.

Here are some pictures of Atoms

Drawing Atoms To draw an atom correctly, you need to use the Periodic Table of Elements.

How to use the table for drawing atoms Atomic # = # Protons = # Electrons

Let’s practice!! The 1 st Element on the Periodic Table is Hydrogen. It has an Atomic # of 1, so it has ___ Proton and ___ Electron. Nucleus with 1 proton 1 st shell 1 Electron

Using your periodic table, can you guess which element this is?

Drawing larger atoms After Hydrogen and Helium, we have to add another shell to put electrons on. Why??? Because: The 1 st shell only holds 2 electrons. All other shells want to hold 8 electrons. Practice drawing Lithium, Berrylium, Boron, and Carbon.

How do we find # of Neutrons? We know that the Atomic # = # Protons and # Electrons, but how do we find # of Neutrons? It’s easy! Take the Atomic Mass # and subtract the Atomic #. (A.M.- A. # = # of Neutrons) What is the # of Nuetrons for Carbon?

Practice makes perfect! On a piece of computer paper, draw electron configurations for the 1 st 20 elements. Note the name of each, symbol for each, the atomic number, protons, neutrons, and electrons.

Using the Periodic Table

Periodic Computer Research Your assignment is to learn all you can about the periodic table as you complete the packet provided. You will need to copy down the web address to find the answers

After your research… You will be responsible for picking one element on the periodic table and presenting on its properties. Include a diagram of an atom, with all parts labeled correctly, something interesting about the element, where it is located on the periodic table, and any other relevant information pertaining to that element. (50 points)

Do atoms ever combine? Yes! They form compounds. Define a compound. How and why??? It has to do with the # of electrons on the outer shell of the atoms. All electrons in the outer most shell are called Valence Electrons

Bonding There are 2 “rules” that you need to know about atoms. 1. The first shell wants to hold 2 electrons 2. The 2 nd, 3 rd,..shells want to hold 8 electrons

Is this a happy atom?

Covalent Bonding This occurs when atoms share electrons to become stable, or “happy”! The shared pair of electrons provides each hydrogen atom with two electrons in its valence shell

More Examples A molecule of water is formed by a covalent bond. Oxygen has 6 electrons on its outer shell, so it wants _____ more? Hydrogen has 1 on its outer shell, it would like to have ____ more? Can you guess how this bond is drawn?

How do we write the formulas for these molecules? There are chemical formulas, which are the written chemical symbols and their subscripts. Example) water is written H 2 O, this is the chemical formula for water! There are structural formulas which are the atomic drawings for molecules, such as what you drew for water.

Practice (Covalent)! Try drawing a molecule of Hydrochloric Acid, or HCl. Try drawing a molecule of methane, which is CH 4.

More info. On Covalent Bonds Covalent bonds are very strong bonds. It is hard to break a covalent bond. Example, your hair is held together by covalent bonds. It takes energy to break these bonds, and a strand of your hair!

Are there other kinds of bonds? Yes! There are also Ionic Bonds. Ionic Bonds are formed by an attraction of positive and negative charges. Where do the charges come from if the atoms are neutral????

Example of an Ionic Bond Draw the atoms Na and Cl. Notice that Na has 11protons and 11 electrons. This gives Na 1 electron in its outer shell. Is Na happy this way? Notice that Cl has17 protons and 17 electrons. This gives Cl 7 electrons in the outer shell. Is Cl happy?

A solution! If Na could loose an electron, and Cl could gain an electron, they would both be “happy.” This is how Ionic Bonds are formed. An Ionic Bond is formed when electrons are transferred from one atom to another, which results and opposite charges that attract each other.

How are the charges formed? When Na looses its electron, how many electrons does it have now? How many protons does it have? This gives Na and (+) charge. Understanding this, explain how Cl becomes (-) charged. +/- attract, and a molecule of NaCl is formed, which is the molecular formula for Table salt!

More on Ionic Bonding When these atoms lose or gain electrons, they get “new names”. Na is now called Na+ or a (Sodium Ion) Cl is now called Cl- or a (chloride ion) Any positive ion is called a Cation Any negative ion is called an Anion

Practice Problems MgOCaBr 2 LiFBe 3 P 2 PbBr 4 Be 3 N 2 Li I K 2 O

Practice Problems for Homework! Page: 44 #s: 1, 5, 6 P.76: # 3 P. 85: # 1, 3, 4, 5, 7, P.94: # 1, 4, 5,