12 Questions
If an atom has 16 protons, how many electrons does it have?
16
What is the relationship between atomic number and the number of protons in an atom?
They are equal
In an atom with 20 neutrons and an atomic number of 13, how many protons are present?
13
For an atom to be electrically neutral, what must be true about the number of protons and electrons?
They must be equal
What is the relationship between mass number and the total number of nucleons in an atom?
Mass number equals the total number of nucleons
Which subatomic particle determines the chemical properties of an element?
Electron
In complete chemical symbol notation, where is the mass number placed?
As a superscript in front of the chemical symbol
What determines the chemical properties of an atom?
Number of electrons
How do isotopes differ from each other?
Different mass numbers
Which subatomic particle varies in number among atoms of the same element?
Neutrons
For an atom with an atomic number of 20, how many electrons are present if it is a neutral atom?
20
What is the total number of nucleons in an atom with an atomic number of 40 and a mass number of 90?
130
Study Notes
Subatomic Particles
- An electron is a subatomic particle with a negative electrical charge.
- A proton is a subatomic particle with a positive electrical charge.
- A neutron is a subatomic particle with no charge associated with it, making it neutral.
Atomic Structure
- Protons and neutrons are located in the nucleus, which is the small, dense, positively charged center of an atom.
- Electrons are located outside the nucleus, in the electron cloud.
- The nucleus is positively charged due to the presence of positively charged protons.
- An atom has no net electrical charge, as the number of positive and negative charges must be equal.
Charge and Mass Characteristics
- Electrons have a negative charge and a small mass.
- Protons have a positive charge and a larger mass than electrons.
- Neutrons have no charge and a slightly larger mass than protons.
Atomic Number and Mass Number
- The atomic number (Z) is the number of protons in the nucleus of an atom.
- The atomic number also specifies the number of electrons in an atom.
- The mass number (A) is the total number of protons and neutrons in the nucleus.
Calculating Subatomic Particles
- Number of protons = atomic number (Z)
- Number of electrons = atomic number (Z)
- Number of neutrons = mass number (A) - atomic number (Z)
Isotopes
- Isotopes are atoms of an element with the same atomic number but different mass numbers.
- Isotopes have the same number of protons and electrons but differ in the number of neutrons.
Atom Size Relationships
- The nucleus is extremely small, with a radius of about 1/100 000 of the total radius of the atom.
- The size of the nucleus is comparable to a baseball (about 2.9 inches in diameter).
Test your knowledge about the characteristics and arrangement of subatomic particles like electrons, protons, and neutrons within an atom. Learn about their charges, masses, and locations within the atom.
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