Chapter 4

1. 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 • ___________ - 1897 atoms have negatively charged electrons embedded in a positive sphere. • _______ - negatively charged particles JJ Thomson electrons

6. Rutherford and the Nucleus • 1911 - ____________ - 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 • ___________ - 1913, 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 • 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