sci 5.1

5) How reactive are the elements in Group 18? Explain this reactivity in terms of the number of valence electrons.

Because the Group 18 elements have eight valance electrons (except for helium with two) they are stable. They seldom transfer electrons to other atoms or share electrons with other atoms. So noble atoms do not react very easily with other elements to form compounds

2) Do oxygen atoms become more stable or less stable when oxygen forms compounds? Explain.

Oxygen is more stable in a compound (like in water-H2O) because alone oxygen only has 6 valence electrons (and it wants 8 to be stable). But in a compound like water, it can have 8 because each hydrogen shares its valence electron.

4) Why do the properties of elements change in a regular way across a period?

The properties change in a pattern because the valence electrons change in a repeating pattern and valence electrons determine properties.

29) in naming ionic compounds, the name of the ----------- is first followed by the name of the _________

cation is first onion is second

28) 3 qualities of an ionic compound

crystalline high melting point conduct electricity when melted

6) valence electrons

highest energy level held together most loosely located in the outer shell the only ones transferred or shared with other atoms

10) Elements with full valence shells are reactive or nonreactive?

nonreactive

7) electron dot diagram

shows symbols for the element surrounded by dots. each dot stands for 1 valence electron

30) compounds are represented by chemical formulas that show what?

that show the ratio of the elements that compose them

9) why are valence electrons so important?

The number of valence electrons in an atom determines many properties of the element

3) Summarize how the periodic table is organized, and tell why this organization is useful.

The periodic table is organized by atomic number (which is the number of protons in an element). Each family/period/column has the same number of valence electrons (and similar properties). This information is useful because the valence electrons determine how and with what an element will bond because valence electrons determine bonding.

1) What role do valence electrons play in the formation of compounds from elements?

Valence electrons are the electrons that have the highest energy level and are held most loosely (because farthest from the nucleus). Valence electrons are what control how each element bonds (so what kind of compounds it forms).

23) atoms with 1,2,3 valence electrons will give away their valence electrons to look like ______?

a noble gas

24) atoms with 5,6,7 valence elctrons will steal valence electrons to look like ________"

a noble gas

13) Ion

an atom or group of atoms that has an electric charge due to the loss or gain of electrons

12) Where do you place the Lewis dots once you have the number of electrons?

around the elements atomic symbol

19) anions

have a negative charge due to the gain of electrons

20) cations

have a positive charge due to the loss of electrons

11) What do you need to know to draw a Lewis Dot?

how many electrons are in the outer shell

14) polyatomic ion

ions that are made of more than one atom a group of atoms that react as a unit

17) chemical formula

is a combination of symbols that shows the ratio of elements in a compound

15) ionic bond

is the attraction between two oppositely charged ions

22) What happens when an atom gains valence electrons?

it becomes negatively charged

21) what happens when an atom loses valence electrons?

it becomes positively charged

16) ionic compound

it consists of positive and negative ions such as sodium chloride

25) ionic bonds form from electrical attractions between _____ and _______?

onions and cations

27) ionic compounds consist fo a combination of onions and cations in which the bonding balances out the ________ and _________ charge

positive and negative

26) polyatomic ions are made of several atoms and have an overall ------------- or --------------- charge

positive or negative

8) chemical bond

the force of attraction that holds 2 atoms together as a result of the rearrangement of electrons between them

18) Crystal

the ions form an orderly three dimensional arrangement

31) subscript

the number of atoms of each element in the compound