Science Unit 3, Lesson 3

The first energy level can hold, at most, ______ electron(s).

2

How many valence electrons does oxygen have? How do you know?

6; since oxygen is number eight on the Periodic Table, an oxygen atom would have eight protons and eight electrons. Remember that you have to fill the first energy level before moving to the second energy level. Two electrons fit in the first energy level. There are six electrons left. These electrons fit in the second level, making this the outermost energy level. The electrons in the outermost energy level are valence electrons, so oxygen has six valence electrons.

The second energy level can hold, at most, _________ electron(s).

8

What is an example of elements forming bonds?

A chlorine atom has seven valence electrons. It needs one more electron to have a full outermost energy level. A chlorine atom can gain one electron from a sodium atom. When this happens, the chlorine atom becomes a negative ion.. The sodium atom that loses the electron becomes a positive ion. The ions formed by chlorine and sodium both have eight valence electrons. They have full outermost energy levels. Bonds hold the negative and positive ions together. The resulting substance is sodium chloride, also known as table salt. ​

How many valence electrons do elements in groups 1-18 have?

A. Group 1 ~~~ 1 valence electrons B. Group 2 ~~~ 2 valence electrons C. Groups 3-12 ~~~ no simple rule D. Group 13 ~~~ 3 valence electrons E. Group 14 ~~~ 4 valence electrons F. Group 15 ~~~ 5 valence electrons G. Group 16 ~~~ 6 valence electrons F. Group 17 ~~~ 7 valence electrons G. Group 18 ~~~ 8 valence electrons (except for helium, which has two)

What is the formula to find the amount of electrons in each energy level?

E stands for energy level. E squared times two: (E x E) x 2

space-filling model

In this model, atoms are represented as solid spheres. The spheres do not show the parts that make up the atoms, yet it clearly shows how the atoms are connected to each other.

What is an example of atoms being rearranged?

The changing of colors of leaves in fall is the result of chemical changes. Leaves contain pigments of different colors, such as red, yellow, and green. Usually leaves appear green because they have a larger amount of green pigment. In the fall, the atoms that make up the green pigment are rearranged to form new, colorless substances. You can see the red and yellow pigments because they do not break down as easily.

Do chemical changes change the identity of a substance? Does a chemical change create or destroy atoms?

Yes, chemical changes do change the identity of a substance. However, during a chemical change, atoms are neither created nor destroyed. Instead, the atoms are rearranged to make new substances with different properties.

Does helium have a full outermost shell? Explain.

Yes, for it only has two electrons, and the first energy level fits no more than two electrons, which means that those two electrons are helium's valence electrons and that as a result, helium has a full outermost shell.

ion

a charged particle that forms when an atom loses or gains an electron

molecule

a group of atoms that are held together by chemical bonds

dot diagram

a simple diagram that uses dots to represent the valence electrons of an atom or ion

What is an example of a molecule?

a water molecule; every water molecule is made up of one oxygen atom bonded to two hydrogen atoms. The chemical bonds hold the atoms together.

chemical bond

an interaction that holds atoms or ions together

Why do scientists use models of the atoms to show how atoms behave?

because atoms are too small to be observed directly.

What has to occur for atoms to be rearranged? What is an example of this?

chemical bonds have to be formed or broken; for example, to form hydrogen chloride, initially there are bonds between the hydrogen atoms and bonds between the chlorine atoms. These bonds break, and a new bond forms between each hydrogen atom and chlorine atom. The atoms that make up the hydrogen and chlorine do not change their identity. Instead, the atoms are rearranged.

Scientists use _________ models depending on what they need to study. For example, _____________________.

different; the way a model shows electrons is important because electrons are involved in chemical bonding.

valence electrons

electrons found in the outermost energy level of an atom

Elements in the same _________ have the same number of valence electrons.

group

electron cloud model

shows how electrons are found in a region around the nucleus. It helps show the general location of the different parts of the atom, yet it does not show the number of electrons.

Bohr model

shows the number of electrons in an atom. The electrons are shown as dots placed in rings around the nucleus. Bohr models do not show the true arrangement of electrons in the atom. Each ring represents an energy level, not a physical location in the atom. However, showing electrons in energy levels helps predict how and why atoms form chemical bonds.

Each energy level can hold a _________ number of electrons.

specific

What are four common types of models to represent atoms?

the electron cloud model, the Bohr model, the space-filling model, and the dot diagram

Which elements have a full outermost energy level?

the elements in Group 18

Electrons are usually not added to higher energy levels until ______________________.

the lower ones are filled

What is the energy level furthest from the nucleus called?

the outermost energy level

Are elements in Group 18 reactive or unreactive? Explain.

unreactive because typically, the elements that react to form bonds are those with a not full outermost energy level. Through forming bonds, elements gain, lose, or share electrons to have a full outermost shell.