Unit 1 B.6, B.7, B.8, B.9

Elements on the periodic table are grouped according to their similar properties.  Horizontal rows on the periodic table are called periods and columns are called groups or families.  The alkali metal family consists of six elements: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).  These elements are all highly reactive metals that form a chloride compound with a 1:1 alkali metal atom to chlorine atom ratio and an oxide with a 2:1 alkali metal atom to oxygen atom ratio.  Another family is the noble gas family.  The gases in this group are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).  These gases are known to be very unreactive.  In the column to the left of the noble gases is the halogen family, a group containing fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).  When elements in the halogen group form compounds, they are known as halide compounds.  The halogen gases are highly reactive and readily form binary compounds with hydrogen.  The arrangement of the periodic table is useful because it groups elements according to their key characteristics.  It can help scientists determine properties of any element in a chemical family because of the other related elements.  An element’s properties can be determined by averaging the properties of the elements directly and directly below it.  Chemical formulas can also be predicted in the same manner.

Unit 1 B.3, B.4, B.5

In “The Electrical Nature of Matter”, we learned about the relationship between chemical bonds and atoms.  While like charges repel, unlike charges attract.  Every electrically uncharged atom has an equal amount of protons (positively charged particles) and electrons (negatively charged particles).  Also, some atoms have one or more neutron, or electrically neutral particle.  Attractions between positive and negative charges by the particles hold atoms together.  In the most recent periodic table, an element’s atomic number determines its position on the table.  An element’s atomic number is the amount of protons present.  Although earlier periodic tables were organized by an element’s mass number, or the combined mass of the protons and neutrons in the nucleus, the neutron made it difficult to record massive atoms.  All atoms of a certain element have the same number of protons, but the number of neutrons varies from atom to atom.  Isotopes are atoms with the same amount of protons, but with a varying amount of neutrons.

Unit 1 Section B Summary HW Problems Pt. 2

#6:

a. 12

b. 12

c. 12

d. 13

e. 12

f. 14

#7:

An electron is about 1/2000 the mass of a proton or neutron.

#8:

No, the element’s mass number alone is not enough information to prove that the element exists because there is no way to distinguish the amount of protons from just the mass number.

#9:

a. Period

b. Group

#10:

Sodium and potassium.

#2:

Unit 1 Section B Summary HW Problems Pt. 1

#1:
a. 6
b. 13
c. 82
d. 17

#2:
a. no
b. no
c. yes
d. no

#3:

#4:

You cannot change the number of protons in an element, or it changed the element completely.  The student would have to take away 2 electrons rather than add 2 protons.

#5:
a. 12, 13, 41, 195, 238
b. Carbon

Unit 1 B.1, B.2

In the 1800s, scientists had discovered about 60 elements.  They were trying to figure out the bet way in which to organize them by placing the elements with similar properties near each other on a chart.  A Russian chemist named Dimitri Mendeleev published a periodic table with a layout similar to a monthly calendar.  In the 1800s, two characteristics determined the organization of periodic tables: the element's average atomic mass (which is a physical property) and it's "combining capacity" (which is a chemical property).  In the early periodic tables, elements that had similar chemical properties were put into columns together, while increasing atomic masses decided the rows.  Therefore, the elements on the left hand side of the table were very reactive while the elements on the right were not.

Unit 1 Section A Summary HW Problems Pt. 4

#18:
An inference is an educated guess.

#19:
a. Observation
b. Inference
c. Inference
d. Observation
e. Observation
f. Inference

#20:
It is important to organize laboratory observations so that the group can keep track of what reacted with what, and record exactly what happened during their lab.

#21:
It is necessary to read an entire investigation before beginning laboratory work so that you know exactly what you are doing. This is also for the safety of you and the ones working with you.

#22:

#23:

#24:

#25:

#26:

When a model has limitations, it means that it isn't capable of showing the entire picture.  It only shows one small segment of what it is portraying.

A. 10 Paragraph

Elements are classified into three different categories: metals, nonmetal, and metalloids.  Some examples of metal elements are iron (Fe), zinc (Zn), copper (Cu), and tin (Su).  Nonmetals are (as you could probably guess) an element that is not a metal.  This includes carbon (C) and oxygen (O).  Finally, metalloids have both metallic and nonmetallic properties.  Examples of metalloids are silicon (Si) and germanium (Ge).  Metals are commonly ductile, conductive, and malleable, meaning that it flattens without shattering when struck.  Nonmetals are nonconductive and are brittle, meaning that they can shatter into pieces.  These qualities decide where certain elements will be used.