Basic Quiz For 7th Grade Science Elements

Explanation
The energy level closest to the nucleus is called the first energy level or the K shell. According to the Aufbau principle, this energy level can hold a maximum of 2 electrons. Therefore, the correct answer is 2.

Explanation
Neon has 8 valence electrons. Valence electrons are the electrons in the outermost energy level of an atom. Neon belongs to the noble gas group, which means it has a full outer electron shell. In the case of Neon, its outermost energy level is the second energy level, which can hold a maximum of 8 electrons. Therefore, Neon has 8 valence electrons.

Explanation
Silicon is classified as a metalloid. Metalloids are elements that have properties of both metals and nonmetals. Silicon shares characteristics with both metals and nonmetals, making it a metalloid. It is a semiconductor, meaning it can conduct electricity under certain conditions, but not as effectively as metals. Silicon is also brittle like nonmetals, but it can form alloys with metals and has a metallic luster. These properties make silicon a metalloid.

Explanation
The nucleus of an atom contains protons and neutrons. Protons have a positive charge, while neutrons have no charge. Electrons, on the other hand, are found outside the nucleus in electron shells. They have a negative charge and orbit around the nucleus. Therefore, the correct answer is protons & neutrons.

Explanation
The atomic number of an element represents the number of protons in its nucleus, which is also equal to the number of electrons in a neutral atom. Therefore, by knowing the atomic number of an element, we can determine the number of electrons it has.

Explanation
Metals have three or less valence electrons. Valence electrons are the electrons in the outermost energy level of an atom, and they are responsible for the chemical properties of elements. Metals tend to lose electrons to achieve a stable electron configuration, and since they have a small number of valence electrons, they are more likely to lose them. This loss of electrons forms positive ions, which is a characteristic of metals. Therefore, the correct answer is 3.

Explanation
Phosphorus is a nonmetal because it is located on the right side of the periodic table, in the p-block. Nonmetals generally have properties such as low melting and boiling points, poor conductivity of heat and electricity, and tend to gain electrons in chemical reactions. Phosphorus exhibits these characteristics, making it a nonmetal.