1.
An atomic number of an atom is
Correct Answer
A. The number of protons
Explanation
The atomic number of an atom is defined as the number of protons present in the nucleus of an atom. It is a unique identifier for each chemical element, determining the element's identity and its position on the periodic table. The number of neutrons, or the sum of protons and neutrons (called the mass number), is not the atomic number but influences the isotope of the element. For example, all carbon atoms have 6 protons (atomic number 6), but the number of neutrons can vary, forming different isotopes of carbon.
2.
_______ has a positive charge.
Correct Answer
C. Proton
Explanation
A proton has a positive charge because it contains two up quarks and one down quark. The up quarks have a charge of +2/3 each, while the down quark has a charge of -1/3. When combined, the total charge of the proton is +1, making it positively charged. Electrons have a negative charge, neutrons have no charge, and "None of these" is not a valid option.
3.
__________ make up the nucleus of an atom.
Correct Answer
D. Protons and neutrons
Explanation
Protons and neutrons make up the nucleus of an atom. The nucleus is the central part of an atom that contains most of its mass. Protons are positively charged particles, while neutrons have no charge. Together, they form the nucleus and are responsible for the stability and mass of the atom. Electrons, on the other hand, orbit around the nucleus in energy levels.
4.
What is the atomic number of oxygen?
Correct Answer
A. Eight
Explanation
The atomic number of an element represents the number of protons in the nucleus of its atom. Oxygen has an atomic number of 8, which means it has 8 protons in its nucleus. Therefore, the correct answer is Eight.
5.
How many electrons and neutrons does a neutral atom of Carbon-13 have?
Correct Answer
B. 6 electrons and 7 neutrons
Explanation
A neutral atom of Carbon-13 has 6 electrons because the atomic number of carbon is 6, which represents the number of electrons in a neutral atom. Carbon-13 also has 7 neutrons because the mass number is equal to the sum of protons and neutrons, and carbon-13 has a mass number of 13.
6.
What is meant by the mass number of an atom?
Correct Answer
C. The number of protons and neutrons
Explanation
The mass number of an atom refers to the total number of protons and neutrons present in the nucleus of the atom. It does not include the number of electrons as they are found in the electron cloud surrounding the nucleus. The mass number helps in determining the atomic mass of an atom and is an important characteristic of an element.
7.
What is the atomic number of iron?
Correct Answer
A. 26
Explanation
The atomic number of an element represents the number of protons in the nucleus of an atom. In the case of iron, the atomic number is 26, which means that an iron atom has 26 protons. This unique number determines the element's identity and its position on the periodic table. Therefore, the correct answer is 26.
8.
Do you know the atomic mass of copper?
Correct Answer
D. 64
Explanation
The atomic mass of an element refers to the average mass of the atoms of that element, taking into account the different isotopes and their abundance. Copper has two stable isotopes, copper-63 and copper-65, with atomic masses of 62.93 and 64.93 respectively. Since the atomic mass of copper is closer to 64, the correct answer is 64.
9.
What is the atomic mass of oxygen?
Correct Answer
B. 16
Explanation
The atomic mass of oxygen is 16. This is because the atomic mass represents the average mass of all the isotopes of an element, taking into account their abundance. Oxygen has three naturally occurring isotopes: oxygen-16, oxygen-17, and oxygen-18. However, oxygen-16 is the most abundant isotope, making up about 99.76% of all oxygen atoms. Therefore, the atomic mass of oxygen is closest to the mass of oxygen-16, which is 16 atomic mass units (amu).
10.
What would be the atomic number of an atom with 3 protons, 4 neutrons, and 3 electrons?
Correct Answer
C. 3
Explanation
The atomic number of an atom is determined by the number of protons it has. In this case, the atom has 3 protons, which means its atomic number is 3. The number of neutrons and electrons does not affect the atomic number.