Gold 8 Weblog

Elements are arranged in order by the number of their protons (atomic number).

Periods:

• Each row of the periodic table is a different period.
• Periods are numbered 1 through 7.
• Each element in a period has the same number of energy levels (elements in period 1 have 1 energy level, elements in period 2 have 2 energy levels, etc.).

Groups:

• Each column of the periodic table is a different group.
• Groups are numbered 1 through 18 (this is the modern way of numbering groups, many Periodic Tables still use an older method of roman numerals and letters to label the groups).
• Each element in a group (not including transition metals) will have the same number of valence electrons.

• Group 1 elements have 1 valence electron
• Group 2 elements have 2 valence electrons
• Group 13 elements have 3 valence electrons
• Group 14 elements have 4 valence electrons
• Group 15 elements have 5 valence electrons
• Group 16 elements have 6 valence electrons
• Group 17 elements have 7 valence electrons
• Group 18 elements have 8 valence electrons

Metals:

Physical Properties of Metals:

• Luster (shininess)
• Good conductors of heat and electricity
• High density (heavy for their size)
• High melting point
• Ductile (most metals can be drawn out into thin wires)
• Malleable (most metals can be hammered into thin sheets)

Chemical Properties of Metals:

• Easily lose electrons
• Corrode easily. Corrosion is a gradual wearing away. (Example: silver tarnishing and iron rusting)

Non-metals:

Physical Properties of Nonmetals:

• No luster (dull appearance)
• Poor conductor of heat and electricity
• Brittle (breaks easily)
• Not ductile
• Not malleable
• Low density
• Low melting point

Chemical Properties of Nonmetals:

• Tend to gain electrons

Since metals tend to lose electrons and nonmetals tend to gain electrons, metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds. When two or more nonmetals bond with each other, they form a covalent compound.

Metalloids:

Physical Properties of Metalloids:

• Solids
• Can be shiny or dull
• Ductile
• Malleable
• Conduct heat and electricity better than nonmetals but not as well as metals

Parts of an Atom

Nucleus: Center of the atom
-most of mass of atom is located here
-positively charged
-made up of protons & neutrons

Electron: negatively charged particle that surrounds the nucleus in a region

Electron Cloud: Region where electrons are found surrounding the
nucleus

Energy Level: The different areas where electrons move about in an orbit around the nucleus. Closer the orbit, lower the energy
level of the electrons. Further from the nucleus, more energy electrons have.

Proton: positively charged particle with a mass of 1amu located in the nucleus of an atom.

Neutron: particle with no charge, with a mass of 1amu located in the nucleus of an atom

Atomic Number: number of protons in the atom.
Atomic Mass: sum of number of protons and neutrons in the atom.

How to find the number of neutrons in an atom: subtract the atomic number from the atomic mass (make sure you have rounded the atomic mass to the nearest whole number)

How to find the number of electrons in an atom: if an atom is neutral, the number of electrons must equal the number of protons.

Ion: an atom that has gained or lost electrons resulting in a positive or negative charge

Isotope: an atom that has a different number of neutrons in it’s nucleus

Accuracy: how close the measured value is to the true or accepted value. hitting right on the mark

Precision: how close together a group of measurements are to each other.
High precision and low accuracy often indicates a fault in the measuring tool.

Standards: an exact quantity people have agreed to use for comparison.

Measurement Systems:

English: measuring system with no universal pattern. Uses fractions with measurements. Common in USA.
inch, pound, cup, Fahrenheit

Metric: measuring system based on multiples of 10. Uses decimals with measurement. Prefixes with base units.
meter, joule, gram, Celsius

SI: measurement system used worldwide, most commonly with scientists. Similar to metric but with only 7 base units.
kilogram, meter, second, candela, ampere, mol, Kelvin

Metric Prefixes:

kilo- 1000 x base

hecto- 100 x base

deca- 10 x base

base

deci- 0.1 x base (or base divided by 10)

centi- 0.01 x base (or base divided by 100)

milli- 0.001 x base (or base divided by 1000)

Types of Measurement

Length: a measurement of the distance between two points

• SI base unit: meter

Volume: a measurement of the amount of space occupied by an object

• SI base unit: no SI base unit
• Units of measurement: cm³ - solids or mL - liquids
• 1 cm³ = 1mL
• volume of a regular solid = length X width X height
• volume of a liquid = read the lowest point of the meniscus in a graduated cylinder

Mass: a measurement of the amount of matter in an object

• SI base unit: kilogram
• *note* mass and weight are different measurements. Mass does not change with changes in gravity. Weight changes with changes in gravity

A bit about Energy

Energy: the ability to cause change (do work)

The Law of Conservation of Energy: energy is neither created nor destroyed (it does change forms)

Potential Energy: stored energy

Kinetic Energy: energy of motion

• example: a ball thrown straight up loses kinetic energy and gains potential energy until it reaches it’s highest point. The highest point has the greatest potential energy and least kinetic energy. As the ball falls, it gains kinetic energy and loses potential energy.
• *note* the energy in the thrown ball example is transferred from kinetic to potential and back to kinetic again.

Hypothesis: an educated guess; testable prediction.

Theory: an explanation based on many experiments and observations. Example: Big Bang Theory, Kinetic Theory of Matter, Theory of Evolution

Scientific Law: a rule of nature; describes an observation in nature. Example: Newton’s Laws of Motion, Laws of Thermodynamics, Newton’s Law of Universal Gravitation

Problem: a situation where something is missing (written as a question).

Control: a standard used for comparison.

Variable: any part of an experiment that can change.

• Independent Variable: the variable that is changed by the experimenter.
• Dependent Variable: the variable that changes because of the independent variable (the result of the experiment). The DV is measurable.

Constant: any variable that does not change throughout the experiment.