8th-grade Atomic Structure And The Periodic Table

A neutral chlorine (Cl) atom contains 17 electrons. This is because the atomic number of chlorine is 17, which represents the number of protons in the nucleus of an atom. In a neutral atom, the number of electrons is equal to the number of protons, so a chlorine atom has 17 electrons.

The central part of an atom is called the nucleus. It is composed of protons and neutrons, which are tightly packed together. The nucleus carries most of the mass of the atom and is positively charged due to the presence of protons. Electrons, on the other hand, orbit around the nucleus in specific energy levels. Therefore, the correct answer is nucleus.

The electric charge on a proton is positive. Protons are subatomic particles found in the nucleus of an atom and they carry a positive charge. This positive charge is equal in magnitude but opposite in sign to the negative charge carried by electrons. The charge on a proton is fundamental and does not change.

Isotopes of an element have the same number of protons but different numbers of electrons. Since nitrogen has an atomic number of 7, it means it has 7 protons. The isotope in question contains seven neutrons, which means it has a total of 14 nucleons (7 protons + 7 neutrons). Therefore, the correct answer is nitrogen-14.

The elements in Group 1 of the periodic table are commonly called alkali metals because they have similar chemical properties and react vigorously with water to form alkaline solutions. These metals include lithium, sodium, potassium, rubidium, cesium, and francium. They are highly reactive and have low melting points and densities.

The number above the symbol for each element represents its atomic number. The atomic number is a unique identifier for each element and represents the number of protons in the nucleus of an atom. It determines the element's position in the periodic table and provides information about its chemical properties. The atomic number remains constant for each element and is crucial in understanding the structure and behavior of atoms.

The atomic number is the number of protons in the nucleus of an atom, which determines the element's identity on the periodic table. For example, hydrogen has an atomic number of 1, meaning it has 1 proton, while carbon has an atomic number of 6, indicating 6 protons. The atomic number is unique to each element and defines its chemical properties, distinguishing it from other elements.

The modern periodic table is organized by atomic number because it represents the number of protons in an atom's nucleus. The atomic number determines the element's identity and its position in the periodic table. Elements are arranged in increasing order of atomic number, which allows for a systematic organization of elements with similar properties in the same columns or groups. This arrangement helps scientists to understand and predict the behavior and characteristics of different elements based on their atomic number and position in the periodic table.

Ga (Gallium) is the correct answer because it is the only element in Period 4, Group 13. Na (Sodium) is in Group 1, Al (Aluminum) is in Group 13 but in Period 3, and K (Potassium) is in Group 1. Therefore, Ga is the only element that meets the criteria given in the question.

Elements in a group have similar chemical properties because they have the same number of valence electrons. Valence electrons are responsible for the chemical behavior of an element, and elements in the same group have the same number of valence electrons. This similarity in electron configuration leads to similar chemical reactivity and bonding patterns, resulting in similar chemical properties among elements in a group.

The elements on the far right of the periodic table (He, Ne, Ar, and Kr) have full valence electron shells, which makes them stable and less likely to react with other elements. This is because they have achieved a stable electron configuration, either by having a complete outermost energy level (He) or by having a complete octet (Ne, Ar, and Kr). Due to their stable electron configurations, these elements do not generally participate in chemical reactions with other elements.

The half-life of an isotope refers to the amount of time it takes for half of a sample of that isotope to decay. In this case, the half-life of nitrogen-13 is 10 minutes. This means that after 10 minutes, half of the initial 40 grams (20 grams) will have decayed. After another 10 minutes (20 minutes in total), another half of the remaining 20 grams will decay, leaving 10 grams.

Elements in a period have a wide range of chemical properties because they have different numbers of valence electrons, which determine their reactivity and ability to form chemical bonds. Additionally, elements in a period have different electron configurations, resulting in variations in their atomic sizes, ionization energies, and electronegativities. These differences in chemical properties allow elements in a period to exhibit diverse behaviors and reactions with other elements.

When an atom gains one or more electrons to become a negative ion, the extra electrons increase the electron-electron repulsion, causing the electron cloud to expand. As a result, the negative ion becomes larger in size compared to the original atom.

As we move from left to right in a period, the size of the atom decreases. This is because the number of protons and electrons increases, leading to a stronger attraction between the positively charged protons in the nucleus and the negatively charged electrons. This increased attraction causes the electron cloud to be pulled closer to the nucleus, resulting in a smaller atomic size.