Atomic Structure Standards to be covered HSPS 1

Atomic Structure Standards to be covered: HS-PS 1 -1. Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms. HS-PS 1 -2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

Let’s get down to the basics… • An atom is not the smallest particle of matter! • All atoms are made up of subatomic particles which are identical in all atoms Label the Atom!! Protons & Neutrons found in the nucleus • Protons (+) which are positively charged • Neutrons (0) which have a neutral charge • Electrons (-) which are negatively charged Electrons found In orbitals around The nucleus

Using the periodic table to determine the number of subatomic particles in atoms: • Atomic Number • The number of protons in an atom determines the identity and to a large extent the chemical properties of an atom. In a neutral atom the number of electrons is equal to the number of protons. • Atomic Mass • number of protons + number of neutrons in the nucleus. Electrons have little to no mass and therefore do not count towards the atomic mass. Using this example this element has: Protons: _______ Electrons: _______ Neutrons: ____

Let’s try some examples… Determine the number of electrons, protons and neutrons for the following elements: Protons: _______ Electrons: ______ Neutrons: ______

Review from the last class… • Atoms are made of 3 subatomic particles. • Protons & neutrons Are found in the nucleus • Electrons are found in orbitals outside of the nucleus

Bohr Diagrams • Simple diagram which shows the locations of all electrons, neutrons and protons in the element. • All protons and neutrons are found in the nucleus and must always be recognized by writing the number of them in the nucleus. • Electrons will be shown in shells or rings on the outside

Electrons in a Bohr Diagram • The maximum number of electrons in each ring is predetermined. • Each shell of the diagram corresponds with the row on the periodic table. • The electrons in the outer most ring of your element are the valence electrons.

Remember to use your periodic table!!! Any elements in the top row (H & He) have one shell. Any elements in the second row (Li, Be, B, etc) have two shells.

Let’s try an example. Follow these steps: P= 3 N= 4 1. Determine the number of electrons, protons and neutrons. P=__3___ N=_4____ E=_3_____ 2. Create your nucleus. Write the number of protons and neutrons in the this area. 3. Determine how many shells your element will have. Li is on the second row so it will have 2 rings. 4. Determine the number of electrons in each ring and add them to your drawing.

Try another example.

Lewis Dot Diagram • This is a diagram that shows the element symbol and the valence electrons only. • Valence electrons are found in the outermost shell. Let’s see an example. Here is the Bohr diagram for Nitrogen. How many electrons are in the outermost shell? 5 Therefore this is the Lewis Dot Diagram for N.

Remember to use your periodic table!! • The column the element is found in determines the number of valence electrons.

Example time! Create Lewis Dot Diagrams for the following elements: Xenon Boron Radium

Ions! • Ions are elements that do not have the same number of protons and electrons • Because of this they have a charge. • If an ion has more electrons than protons it will be negatively charged. • If an ion has more protons than electrons it will be positively charged. • Ions want a full valence shell • • Shell one’s full valence shell is 2 electrons Shell two’s full valence shell is 8 electrons • To gain a full valence shell ions will lose or gain electrons. • The ionic charge is determined by the number of valence electrons.

Ions Continued • Here is the example of sodium (Na). Sodium has 1 valence electron. If it gets rid of it then it will have a full outer shell. • Sodium will then drop its 1 valence electron and will now have 11 protons and 10 electrons. • This gives it the charge of +1. This is written as Na 1+

Some more examples…. • Chlorine has 7 valence electrons and needs only one to have a full outer shell. Chlorine will add one electron and now have a charge of -1. • This is written as Cl 1 -.

Remember to use your Periodic Table

Practice Time Determine the ionic charge for the following ions…. Sulfur (S) S 2 - Potassium (K) K 1+ Aluminum (Al) Al 3+

Chemical Bonding Chemical bonding occurs when two or more atoms interact with each other using their valence electrons due to their electronegativity. Atoms are most stable when their valence electron shell is full. Three main types of bonding: 1. Covalent Bonding 2. Ionic Bonding 3. Hydrogen Bonding

Covalent Bonding -electrons are shared equally between two atoms -occurs between two elements that are similar in electronegativity

Example: O 2. . . Complete the covalent bonding for the following compounds: H 2 CH 4 N 2 H 2 O

Ionic Bonding -occurs between two atom that have such a high difference in their electronegativity, an electron is transferred from one valence shell to the other. -one atom donates an electron, one atom receives an electron -the resulting atoms will be charged, and attract together

Example: Ca. Cl 2 Complete the following ionically bonded compounds using Lewis Dot Structures: K 2 S Ba. O Al 2 O 3