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In studying the periodic table, you might have noticed something about the atomic masses of some of the elements. Element 43 (technetium), element 61 (promethium), and most of the elements with atomic number 84 (polonium) and higher have their atomic mass given in square brackets. This is done for elements that consist entirely of unstable, radioactive isotopes (you will learn more about radioactivity in the nuclear chemistry chapter). An average atomic weight cannot be determined for these elements because their radioisotopes may vary significantly in relative abundance, depending on the source, or may not even exist in nature. The number in square brackets is the atomic mass number (and approximate atomic mass) of the most stable isotope of that element.

Key concepts and summary

The discovery of the periodic recurrence of similar properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing atomic number in rows known as periods and columns known as groups. Elements in the same group of the periodic table have similar chemical properties. Elements can be classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1–18 from left to right. The elements in group 1 are known as the alkali metals; those in group 2 are the alkaline earth metals; those in 15 are the pnictogens; those in 16 are the chalcogens; those in 17 are the halogens; and those in 18 are the noble gases.

Chemistry end of chapter exercises

Using the periodic table, classify each of the following elements as a metal or a nonmetal, and then further classify each as a main-group (representative) element, transition metal, or inner transition metal:

(a) uranium

(b) bromine

(c) strontium

(d) neon

(e) gold

(f) americium

(g) rhodium

(h) sulfur

(i) carbon

(j) potassium

(a) metal, inner transition metal; (b) nonmetal, representative element; (c) metal, representative element; (d) nonmetal, representative element; (e) metal, transition metal; (f) metal, inner transition metal; (g) metal, transition metal; (h) nonmetal, representative element; (i) nonmetal, representative element; (j) metal, representative element

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Using the periodic table, classify each of the following elements as a metal or a nonmetal, and then further classify each as a main-group (representative) element, transition metal, or inner transition metal:

(a) cobalt

(b) europium

(c) iodine

(d) indium

(e) lithium

(f) oxygen

(h) cadmium

(i) terbium

(j) rhenium

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Using the periodic table, identify the lightest member of each of the following groups:

(a) noble gases

(b) alkaline earth metals

(c) alkali metals

(d) chalcogens

(a) He; (b) Be; (c) Li; (d) O

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Using the periodic table, identify the heaviest member of each of the following groups:

(a) alkali metals

(b) chalcogens

(c) noble gases

(d) alkaline earth metals

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Use the periodic table to give the name and symbol for each of the following elements:

(a) the noble gas in the same period as germanium

(b) the alkaline earth metal in the same period as selenium

(c) the halogen in the same period as lithium

(d) the chalcogen in the same period as cadmium

(a) krypton, Kr; (b) calcium, Ca; (c) fluorine, F; (d) tellurium, Te

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Use the periodic table to give the name and symbol for each of the following elements:

(a) the halogen in the same period as the alkali metal with 11 protons

(b) the alkaline earth metal in the same period with the neutral noble gas with 18 electrons

(c) the noble gas in the same row as an isotope with 30 neutrons and 25 protons

(d) the noble gas in the same period as gold

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Write a symbol for each of the following neutral isotopes. Include the atomic number and mass number for each.

(a) the alkali metal with 11 protons and a mass number of 23

(b) the noble gas element with 75 neutrons in its nucleus and 54 electrons in the neutral atom

(c) the isotope with 33 protons and 40 neutrons in its nucleus

(d) the alkaline earth metal with 88 electrons and 138 neutrons

(a) 11 23 Na ; (b) 54 129 Xe ; (c) 33 73 As ; (d) 88 226 Ra

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Write a symbol for each of the following neutral isotopes. Include the atomic number and mass number for each.

(a) the chalcogen with a mass number of 125

(b) the halogen whose longest-lived isotope is radioactive

(c) the noble gas, used in lighting, with 10 electrons and 10 neutrons

(d) the lightest alkali metal with three neutrons

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Questions & Answers

what is the 3d-orbital of Ti³+
Timi Reply
What is Lewis acids
Yabsra Reply
Lewis acid is any substance, such as the H+ ion, that can accept a pair of nonbonding electrons. In other words, a Lewis acid is an electron-pair acceptor. 
betuel
Thanks
Yabsra
🤜🤛
betuel
🤜🤛
betuel
describe the way of seperation of water and kerosene
Tang Reply
Kerosene is a hydrocarbon and non-polar. Water is a polar molecule. So a mixture of both liquids is immicible and by adding them to a separation funnel, you can open the tap flowing the less dense liquid in a container. You can read on bond polarity and separation techniques on Google.
Abdelkarim
kerosene will never with water cos its a immiscible liquid
SUNDAY
what is Chemistry
Papie Reply
Chemistry is a branch of natural light science
Yabsra
10 sentences discussing factors affecting solubility
Sara Reply
why is chemistry a science subject
Ukwumonu Reply
10 sentences discussing factors affecting solubility
Sara
How to name carbonique Atom
lix Reply
how many period do we have in the period table
Joseph Reply
187
Ukwumonu
how do i do ionic equations
Amantle Reply
what is the formula for alkanes
Amantle
CnH2n+2 is the alkane formula.
Walter
whenever you get off your fat arse
then you can start to do some real work
hmm
gabson
How much sodium hydroxide must be dissolved in 100mL of water to prepare a 3.95molL^_1
Cindy
what is vast array
benedict Reply
what is Nanoscience
benedict
from health care to manufacturing. Australian academy of science
what is the compound
Yaasmiin
what is Chemistry
Papie
What is array
Yabsra
what will be the total moles of all the molecule present when the different quantities of following gases are mixed together at step 4g of CH4, 22.4 dm3 of oxygen, 11.2dm3 of carbon dioxide and 3.02×10^23 molecules of ammonia.
Soni Reply
0.5 moles of methane and 0.5 mole of sulfur dioxide are mixed together what will be the mass of mixture. a.20g b.40g c.50g d.55g e.60g
Soni Reply
answer;b
Ravina
thnx
Soni
"the halogens are all oxidizing agents" what is the reason for this observation
Kelvin Reply
they are halogens....that is why numbnut 😁
This is not the place to talk down or be rude. Anonymous User keep your comments to yourself if you can't be more respectful.
Dionne
please what is a lightening thunder?
Onimisi Reply
wat are hydrocarbon s
Opio Reply
I think they are molecules that comprise only of hydrogen and carbon atoms ( they are organic if I'm not mistaken)
Mmathabo
am new here can I join
Yeko
yes u can
Benita
❤️
Ukwumonu
hydrocarbons are compunds of carbon and hydrogen but sometimes the hydrogen are replaced by some other elements like oxgen, ammonia and the hydroxyl groups.........thats what leads to the classification and names of hydrocarbons
SUNDAY

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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