Which of these is the smallest particle of an element that can exist?
An atom
A mixture
A compound
A solution
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WhyAn atom is the smallest particle of an element that still has the chemical properties of that element.
2Multiple choice · Easy
What is the relative charge on a proton?
+1
-1
0
+2
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WhyProtons carry a relative charge of +1, electrons carry -1, and neutrons are neutral with a charge of 0.
3Multiple choice · Easy
Which substance is a pure element rather than a compound?
Oxygen (O2)
Water (H2O)
Carbon dioxide (CO2)
Sodium chloride (NaCl)
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WhyOxygen gas (O2) contains only one type of atom, so it is an element; the others contain two or more different elements chemically joined.
4Multiple choice · Easy
Where in an atom is almost all of the mass concentrated?
In the nucleus
In the outer electron shell
Spread evenly throughout the atom
In the empty space around the nucleus
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WhyProtons and neutrons sit in the tiny central nucleus, and they carry virtually all of an atom's mass because electrons have a very small relative mass.
5Multiple choice · Easy
In the modern periodic table, the elements are arranged in order of which property?
Atomic number
Mass number
Number of neutrons
Date of discovery
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WhyElements are placed in order of increasing atomic (proton) number, which puts elements with similar properties in the same group.
6Fill in the blank · Easy
A vertical column in the periodic table is called a , and a horizontal row is called a .
Answer:
group, period
WhyElements in the same group have the same number of outer electrons and similar properties; a period is a horizontal row.
7Multiple choice · Medium
An atom has 11 protons, 12 neutrons and 11 electrons. What is its mass number?
23
11
12
34
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WhyMass number is the total number of protons plus neutrons, so 11 + 12 = 23.
8Multiple choice · Medium
Which statement about isotopes of the same element is correct?
They have the same number of protons but different numbers of neutrons
They have the same number of neutrons but different numbers of protons
They have different numbers of electrons in a neutral atom
They have the same mass number
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WhyIsotopes have the same number of protons (same atomic number) but different numbers of neutrons, giving them different mass numbers.
9Multiple choice · Medium
What is the electronic structure of a neutral chlorine atom (atomic number 17)?
2,8,7
2,8,8
2,7,8
8,8,1
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WhyFilling shells 2, 8 then 8 gives 2,8,7 for the 17 electrons, with 7 electrons in the outer shell.
10Multiple choice · Medium
Why does a sodium atom form a Na+ ion?
It loses one electron to achieve a full outer shell
It gains one electron to achieve a full outer shell
It loses one proton from its nucleus
It gains one neutron
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WhySodium loses its single outer electron to gain a full outer shell, leaving one more proton than electron and so a 1+ charge.
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