1. Elements and the Periodic Table 8th Grade Science
Chapter 4
Elements and the Periodic Table
8th Grade Science

2. Introduction to Atoms
Greek philosopher named __________ - proposed that matter is made up of tiny particles that cannot be made any smaller
________ - means “uncuttable”
_____ - smallest particle of an element
___________ - formed in the 1600’s as a series of models developed from experimental evidence.
Democritus
“Atomos”
Atom
Atomic Theory

3. Atomic Theory
As more experiments were conducted and evidence collected, the theory and models were revised.
________________ - John Dalton, English chemist, inferred that atoms had certain characteristics.
Dalton’s atomic theory is still accepted today!
Atoms were like smooth, hard balls that cannot be broken down
Dalton’s Atomic Theory

4. Summary of Dalton’s Ideas page 103
All elements are composed of atoms that cannot be ______.
All atoms of the same element are exactly alike and have the same ____.
An atom of one element cannot be _________ into an atom of a different element – only rearranged.
Every ________ is composed of atoms of different _________ combined in a specific ________.
divided
mass
changed
compound
elements
ratio

5. Thomson Model
___________ atoms have negatively charged electrons embedded in a positive sphere.
_______ - negatively charged particles
JJ Thomson
electrons

6. Rutherford and the Nucleus
____________ - a student of Thomson, found evidence that contradicted Thomson’s model.
______________ - beam of positively charged particles aimed at a thin sheet of gold foil. Most of the particles passed through the foil as expected. However, a few particles were _______.
Ernest Rutherford
Gold Foil Experiment
deflected

7. Conclusions from the Foil Experiment
Since like charges _____ each other, Rutherford concluded that an atom’s _________ charges must be clustered in the _____ of the atom.
______ - center of the atom
________ - no mass
________ - positively charged particles that have mass and are located in the nucleus of the atom.
repel
positive
center
nucleus
electrons
protons

8. Rutherford’s Model

9. Bohr’s Model
___________ , Danish Scientist, student of both Thomson and Rutherford – electrons move around the nucleus in certain _____ based on energy levels.
Bohr’s Model resembles planets orbiting the sun or layers of an onion.
Neils Bohr
orbit

10. Cloud of Electrons 1920’s – atomic model changed again
Scientists determined that electrons DO NOT orbit the nucleus like planets.
_________ can be anywhere in a cloudlike region around the __________.
An _______ movement is related to its _________ - specific amount of energy that it has.
____________ affects the atoms reactions with other atoms.
Electrons
nucleus
electrons
Energy level
Energy level

11. The Modern Atomic Model
___________ discovered another particle in the nucleus of atoms.
_________ - particle discovered by Chadwick that has no electrical charge and nearly the same mass as _______.
_______________ - consists of a nucleus that contains protons and neutrons surrounded by a cloudlike region of moving electrons.
James Chadwick
Neutrons
Protons
Modern Atomic Model

12. Particle Charges
In an tom the number of ________ equals the number of __________.
_________ have a positive charge and a ____
_________ have a negative charge and very little _______.
_________ have neutral charge and a mass that equals that of protons.
________ charge of ________ equals the ________ charge of _________.
protons
Electrons
mass
Protons
electrons
mass
Neutrons
Positive
Protons
negative
Electrons

13. Masses and Charges Charges balance making the atom neutral
Particle
Symbol
Charge
Relative Mass (amu)
Proton p⁺ 1₊ 1
Neutron n
Electron e⁻ 1₋
1/1,836
Charges balance making the atom neutral
Number of neutrons does not have to equal the number of protons
Neutrons do not affect the charge of an atom because they have no charge
Approximately 2,000 e⁻ equal mass of one proton.

14. Atomic Number
Every atom of an element has the same number of _________.
_____________ - number of protons in the nucleus of an atom.
Atomic number identifies an _________.
_______ - atoms with the same number of protons but a different number of neutrons.
__________-sum of the protons and neutrons in the nucleus of an atom.
protons
Atomic Number
element
Isotopes
Mass number

15. Patterns in the Elements
_____________ - Russian scientist discovered a set of patterns that applied to all elements. Mendelev arranged the elements in order of increasing __________. ____________ - organization of the elements where the properties of the elements repeat in each row of the table. ___________ - Brittish scientist discovered a way to measure the positive charge on an atom’s nucleus – the atomic number.
Dmitri Mendelev
Atomic mass
Periodic table
Henry Moseley

16. Periodic Table of Elements
After Moseley’s discovery, the periodic table was rearranged from ________ to _________.
Properties of an element can be predicted based on its place in the ___________.
Periodic table is arranged according to ___________ increasing from left to right.
________ - horizontal rows on the periodic table where the properties of the elements change in a set pattern.
Atomic mass
Atomic number
Periodic table
Atomic number
periods

17. Organization of the Periodic Table
Elements on the left side of the periodic table are _______________.
Elements in the middle of the periodic table are ______________.
Elements on the right side of the periodic table are _________________.
______ - 18 vertical columns or “families” on the periodic table with similar characteristics such as rate of reaction. (except lanthanides and actinides).
Highly reactive metals
Less reactive metals
Metalloids and non-metals
Groups

18. Reading the Periodic Table
Each element in the periodic table has all of the following:
____________ - number of protons in the nucleus
_____________ - 1 or 2 letter representation
____________
__________ - average mass of all of the isotopes of the element.
Atomic Number
Chemical Symbol
Element Name
Atomic Mass

19. Metals Physical properties of metals: ________
__________ - material can be hammered or rolled into flat sheets and other shapes.
_______ - material can be pulled out or drawn into a thin wire
__________ - ability of an object to transfer heat or electricity to another object.
___________ - metal that is liquid at room temperature
shininess
malleability
ductility
conductivity
Mercury (Hg)

20. Chemical Properties of Metals
_________ - the ease or speed of an element to combine or react to other elements and compounds.
Metals usually react by losing ________ to other atoms.
Sodium (Na) is very reactive where gold (Au) and platinum (Pt) are much less reactive.
__________ - the destruction of a metal because of its reactivity.
reactivity
elements
corrosion

21. Metals in the Periodic Table
_______ of metals decreases from left to right on the periodic table.
____________ - metals in Group 1 on the periodic table that react with other elements by losing one ______.
Alkali metals are never found in __________ elements in nature – only in compounds.
___________________ - two most important alkali metals – important for life processes.
reactivity
Alkali Metals
electron
uncombined
Sodium(Na) and potassium (K)

22. Alkali Earth Metals
______________ - Group 2 on the periodic table that react with other metals by losing two electrons.
Not as reactive as metals in __________ but more reactive than ,most other metals.
Never found uncombined in nature.
______________________ - two most common alkali earth metals.
Alkali Earth Metals
Group 1
Magnesium (Mg) and Calcium (Ca)

23. Other Elements on the periodic table
____________ - elements in Group 3 through 12. These metals are hard and shiny, good conductors of electricity, less reactive than metals in Groups 1 and 2. ________ is an example of a very important transition metal.
_______________ - only some are metals such as aluminum, tin and lead
_________ - two rows of elements at the bottom of the periodic table.
Transition Metals
Iron (Fe)
Groups 13, 14, and 15
Lanthanides

24. Lanthanides
__________ - soft, malleable shiny metals with high conductivity.
Lanthanides mix with other metals to form _____.
_____ - mixture of a metal and at least one other element, usually another metal.
_________ - only four occur naturally on earth – all others were created artificially. These elements are VERY unstable. Ex. Uranium
Lanthanides
alloys
alloy
Actinides

25. Synthetic Elements
____________ - elements that follow uranium that are not found naturally on Earth – when nuclear particles are forced to crash into one another.
_____________ - powerful machines used by scientists to move atomic nuclei to very high speeds.
Synthesized
Particle accelerator

26. Non-metals and Metalloids
Physical properties of non-metals:
______________
_____________________
Many non-metals are common elements on Earth
________non-metals are ______ at room temperature.
___________ - only non-metal that is liquid at room temperature
Poor conductors
Reactive with other elements
Dull and brittle
10 of 16
gases
Bromine (Br)

27. Chemical Properties of Non-Metals
Atoms of non-metals usually _____ or ______ electrons with atoms that they react with.
When metals and non-metals react, _________ move from the metal atoms to the non-metal atoms.
Non-metals can also form compounds with other non-metals.
gain
share
electrons

28. Families of Non-metals
1. _______________ - Group 14 only carbon is a non-metal. atoms that gain, lose, or share ____electrons when reacting with other elements.
2. ______________ - Group 15 contains two non-metals, nitrogen and phosphorous. These atoms usually gain, lose or share _______ electrons when reacting with other elements.
80% of the atmosphere is nitrogen gas (N₂)
The Carbon Family
four
The Nitrogen Family
three

29. Families of Non-Metals continued
3. _____________ - Group 16 contains three non-metals – oxygen, sulfur and selenium. Elements in the oxygen family usually gain or share ___ electrons.
_________ is highly reactive – it can combine with nearly any other element.
Oxygen is the ____ most abundant element in the atmosphere (Nitrogen is first)
The Oxygen Family
two
oxygen
most

30. The Halogen Family
4. ______________ - Group 17 contains flourine, chlorine, bromine, iodine, and astatine (not a non-metal). _______ means “salt forming”. Halogen atoms usually gain or share ____ electron when it reacts with other elements.
All halogens are __________ and can be dangerous to humans.
Many compounds that contain halogens can be useful to humans – salt, flourine in water, calcium chloride.
The Halogen Family
Halogen
one
Very reactive

31. Noble Gases
__________ - elements in Group 18 that do not ordinarily form compounds because atoms of noble gases do not usually gain, lose, or share electrons.
These gases are usually ___________.
All of the noble gases exist in the Earth’s ___________.
Noble gases were not discovered until late 1800’s because they are _______ and ________.
Noble Gases
unreactive
atmosphere
unreactive
scarce

32. Hydrogen __________ - in the upper left corner of the periodic table.
Hydrogen makes up more than ___ of the atoms in the universe.
Hydrogen is rarely found as a ___________.
Hydrogen (H)
90%
Pure element

33. Metalloids
____________ - along the border between metals and non-metals.
There are ___ metalloids and they have characteristics of both metals and non-metals.
All metalloids are ____ at room temperature.
Metalloids are also brittle, hard, somewhat reactive, varying ability to conduct heat and electricity
________ - most common metalloid
Metalloids 7
solid
Silicon (Si)

34. Semiconductors
____________ - substances that conduct electricity under some conditions but not under others.
________ are used as semiconductors because of their physical properties.
Semiconductors are used to make _________, _____________, and ___________.
Semi-conductors
metalloids
lasers
Computer chips
transmitters

35. Radioactive Elements
_____________ - the atomic nuclei of unstable isotopes release fast moving particles and energy.
_____________ - French scientist in 1896 discovered the effects of radioactive decay while he was studying a mineral that contained uranium.
___________ - named after __________ is the spontaneous emission of radiation by an unstable nucleus such as uranium.
Radioactive Decay
Henri Becquerel
Marie Curie
radioactivity

36. Types of Radioactive Decay
Natural radioactive decay can produce ___________, ____________, and ___________.
_________ - an alpha particle consists of two protons and two neutrons and is positively charged. The release of an alpha particle by an atom is decreases the atomic number by __ and the atomic mass by __
Alpha particles
Beta particles
Gamma rays
Alpha decay 2 4

37. Beta Decay
__________ - a neutron inside of the nucleus of an unstable atom changes into a negatively charged beta particle and a proton.
__________ - fast moving electron given off by a nucleus during radioactive decay.
Nucleus has one _____ neutron and one ____ proton – therefore, the atomic mass stays the same but the atomic number increases by __
Beta Decay
Beta particle
less
more 1

38. Gamma Radiation
_____________ - consists of high-energy waves – has no charge and does not cause a change in either atomic mass or atomic number.
Gamma Radiation

39. Effects of Nuclear Radiation

40. Radioactive Isotopes