The atomic number represents the identity of the element and reveals the number of protons, whereas the atomic mass reveals the number of protons and neutrons.
The atom is the fundamental unit of an element and it’s composed of the 3 subatomic particles.
Concept: Discussing Atomic Structure2m
Remember that the basic functional unit in Chemistry is the atom itself. Now, if we want to go deeper into the atom, remember it's composed of three subatomic particles. We're going to say in the center of our atom, the very center of our atom is what we have, that's called the nucleus.
If we take a look at this illustration on the right—that right there what I circled is the nucleus. We're going to say inside the nucleus, we have two out of the three subatomic particles. We have our protons and our neutrons. We're going to say spinning around it, we find the third subatomic particles, so we have the small green negatively charge balls, subatomic particles flying around our nucleus. These are the electrons.
We're going to say that the protons are positively charge. We're going to say that the electrons which are spinning around their nucleus are negatively charge and then we're going to say that the neutrons are non charge subatomic particles. They're neutral, they don't have a charge.
Inside the nucleus we have protons which are positive and neutrons which are neutral. The nucleus overall has a positive charge and then the electrons are spinning around it, the electrons are negatively charged.
Concept: Discussing Atomic Number & Atomic Mass2m
Now, what we're going to say here is we're dealing with two types of information on any given element. We're going to say we have the atomic number and we're going to have the atomic mass, oftentimes called the mass number.
We're going to say that the atomic number uses the variable Z and it equals the number of protons. So, the atomic number tells us the number of protons and also we determine the identity of an element. If you know the number of protons, then you know the element we're talking about, because each element has a specific number of protons. The atomic number kind of, is like the fingerprint for that element.
For example, if you look at periodic table at carbon, you'll see that carbon has associated with it, the number six. That six tells us that carbon has six protons. Carbon is the only element on the periodic table with six protons. Again, remember the atomic number, not only tells us the number of protons, but from that the identity of the element.
Now, we also have the atomic mass, also called the mass number at times. We're going to say it uses the variable A or we're going to say, 'This equals the number of protons and neutrons in an element.' So basically it gives us everything inside of the nucleus. Because remember the nucleus also has protons and neutrons.
Now, if we bring all of this together, we're going to say our element is, we usually use the variable X to represent our element, then we're going to have the atomic mass is A and then right below it is our atomic number. We usually see this kind of notation in class and on your exams.
The number of protons gives the identity of an element. Ions arise when there is an unequal number of protons and electrons.
Example: Identify the unknown element.
Element X (8 protons, 8 electrons, 8 neutrons)
Element Y (35 protons, 36 electrons, 46 neutrons)
Element Z (12 protons, 10 electrons, 13 neutrons)5m
What species is represented by the following information?
p+ = 47 n° = 62 e - = 46
Give the number of protons, the number of neutrons, the number of electrons, and the approximate mass (in amu) for the following particle.
71Ga3+ number of protons : ______ number of electrons : ______
number of neutrons : ______ approximate mass (amu) : ______
The table below describes four atoms. Which atoms represent the same element?
A) A and B represent the same element
B) A and C represent the same element
C) A and D represent the same element
D) B and C represent the same element
E) C and D represent the same element
Consider each of the following statements:
I. An electron has a lower mass than a proton
II. Electrons are found inside the nucleus of an atom
III. A neutral atom will have the same number of electrons as neutrons
Which answer lists all of the true statements above?
A. I only B. II only C. I and II D. I and III E. All three are true
All neutral atoms of tin have 50 protons and 50 electrons. (T/F)
The mass of a neutron is equal to the mass of a proton plus the mass of an electron. (T/F)
An isotope of an element contains 82 protons and 122 neutrons. What is the symbol for the isotope?
The word isoelectronic means having an equal number of electrons. Which of the following statements is/are true below.
a. i & ii
b. i & iii
c. ii & iii
d. i only
e. iii only
Complete the following table by filling in the missing information for each row.
Vanadium can have multiple ions. When vanadium has this symbol:
The atomic number (Z), mass number (A), number of neurons (n) and number of electrons (e) are:
a. Z = 23, A = 51, n = 28, e = 18
b. Z = 51, A = 23, n = 28, e = 23
c. Z = 28, A = 51, n = 28, e = 23
d. Z = 28, A = 23, n = 51, e = 18
Which statement concerning the structure of the atom is correct?
A. Protons and neutrons have most of the mass and occupy most of the volume of the atom.
B. Electrons have most of the mass but occupy most of the volume
C. Electrons have most of the mass but occupy very little of the volume of the atom
D. Protons and neutrons have most of the mass but occupy very little of the volume of the atom.
Which ion has twenty-eight electrons?
What do these have in common?
20Ne 19F- 24Mg2+
A. the same number of protons
B. the same number of neutrons
C. the same number of electrons
D. the same size
What do these have in common?
A. The same number of protons
B. The same number of neutrons
C. The same number of electrons
D. The same size
Osmium has six naturally occurring isotopes. When the most abundant isotope has this symbol:
The atomic number (Z), mass number (A), number of neutron (n) and number of electrons are:
A) Z=76, A=114, n=190, e=76
B) Z=190, A=76, n=114, e=76
C) Z=76, A=76, n=114, e=82
D) Z=76, A=190, n=114, e=70
Which of the following statements is/are TRUE about subatomic particles?
a) An anion has the same number of protons and electrons.
b) Neutrons have the same mass as electrons.
c) Protons and electrons have opposite, but equal in magnitude, charges.
d) Neutrons and electrons are found in the nucleus.
Identify the following element: a halogen whose anion contains 36 electrons.
A. Cl B. Kr C. Rb D. Br
Which of the following is the symbol for the ion with a +4 charge, 30 neutrons and 21 electrons?
1. 55Mn4+ 2. 51Cl4+ 3. 51Mn4+ 4. 58Ni4+
One isotope of a metallic element has a mass number of 65 and 35 neutrons in the nucleus. The cation that this atom forms has 28 electrons. What is the symbol of the cation?
1. 65Zn 2. 65Ga3+ 3. 65Zn2+ 4. 65Ni2+
How many protons, neutrons and electrons are there in the anion 31P3–?
A. 15 protons, 16 neutrons, 12 electrons
B. 16 protons, 15 neutrons, 18 electrons
C. 15 protons, 16 neutrons, 18 electrons
D. 12 protons, 19 neutrons, 15 electrons
E. 15 protons, 16 neutrons, 15 electrons
Consider the species 44 Ca+2. How many electrons, protons, and neutrons does it contain?
a. 20P, 20N, 22e
b. 20P, 20N, 18e
c. 20P, 24N, 18e
d. 20P, 24N, 22e
e. 44P, 44N, 42e
What is the name of the atom that has the atomic number 36?
What is the charge of a Boron (B) ion with 7 electrons?
How many protons are there in a gold (Au) nucleus?
What is the molar mass (g/mol) of a sample of aluminum where all the atoms have 15 neutrons?
e. none of these
A hydrogen-3 cation has...
A. No electrons.
B. The same number of protons and neutrons.
C. Three protons.
D. Two electrons.
E. One neutron.