Atoms and Atomic Structure

A neutral atom has an equal number of protons and electrons. The atomic number of the element, which is 30, indicates that it has 30 protons. Therefore, a neutral atom of this element also contains 30 electrons. The atomic mass of 65.38 does not affect the number of electrons in this case.

An atom with an atomic number of 13 is aluminum, which has 13 electrons in its neutral state. When aluminum forms a 3+ cation, it loses three electrons. Therefore, a 3+ cation of aluminum has 10 electrons.

The central atom in the carbonate ion (CO₃²⁻) is carbon. It is surrounded by three electron domains: one for each of the three bonding pairs of electrons with oxygen atoms. These three domains are arranged in a trigonal planar geometry, with no lone pairs on the carbon atom.

Indium (In) has 46 electrons in total. Its electron configuration is [Kr] 4d¹⁰ 5s² 5p¹, meaning it has 36 core electrons (those in the noble gas configuration of krypton) and 10 valence electrons (from the 4d, 5s, and 5p orbitals). Thus, the number of core electrons in indium is 36.

Shielding occurs in an atom due to the presence of inner-shell electrons. These electrons partially block the attractive force of the nucleus on the outer-shell electrons, reducing the effective nuclear charge experienced by them. As a result, the outer electrons are less tightly held, influencing atomic properties such as size and ionization energy. This effect is crucial for understanding the behavior of elements in the periodic table.

The region that surrounds the nucleus and contains most of the space in the atom is called the electron cloud. This area is where electrons are likely to be found as they move in various orbitals around the nucleus. The electron cloud is not a physical structure but rather a probabilistic representation of where electrons exist, reflecting their wave-like behavior.

The ground state electron configuration of krypton (Kr), which has an atomic number of 36, is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶. This configuration reflects the distribution of electrons across the various atomic orbitals, filling them according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. Krypton is a noble gas, and its full outer electron shell makes it chemically stable and inert.

When one atom gives up an electron to another atom, it forms an ionic bond. The atom that loses the electron becomes a positively charged ion (cation), while the atom that gains the electron becomes a negatively charged ion (anion). The electrostatic attraction between these oppositely charged ions results in the formation of an ionic compound.

To find the number of atoms in 100 grams of lead, we first need to determine the molar mass of lead, which is approximately 207.2 g/mol. Using Avogadro's number (approximately (6.022 \times 10^{23}) atoms/mol), we can calculate the number of moles in 100 grams: (100 , \text{g} \div 207.2 , \text{g/mol} \approx 0.482 , \text{mol}). Multiplying the number of moles by Avogadro's number gives approximately (0.482 , \text{mol} \times 6.022 \times 10^{23} , \text{atoms/mol} \approx 2.90 \times 10^{23} , \text{atoms}) of lead in 100 grams.

The first element that has enough electrons to begin placing in the 3d sublevel is scandium (Sc), which has an atomic number of 21. In its electron configuration, scandium is represented as [Ar] 3d¹ 4s², indicating that the 3d sublevel starts to fill after the 4s sublevel.

The compound 'Fe2O3' has TWO(2) atoms of iron (Fe) and THREE(3) atoms of oxygen.

NB THe number AFTER the elemental symbol indicates the number of atoms of that element present in the compound. Although I cannot show it on 'Answers' , the number should be written 'subscript'.

NNB A number written in front(to the left) of a compound indicates the molar ratio required to react. It is written in normal case.

To calculate the total number of atoms in 6PCl₅, first note that each molecule of PCl₅ contains one phosphorus (P) atom and five chlorine (Cl) atoms. Therefore, in 6PCl₅, you have 6 phosphorus atoms and (6 \times 5 = 30) chlorine atoms. Adding these together gives a total of (6 + 30 = 36) atoms in 6PCl₅.

Strontium (Sr) has an atomic number of 38, which means it has 38 electrons in its neutral state. In the ion Sr²⁺, it has lost two electrons, resulting in a total of 36 electrons. Therefore, Sr²⁺ has 36 electrons.

The element that fits all these criteria is phosphorus (P). Phosphorus has 5 valence electrons, which is more than oxygen (6 valence electrons), fewer than neon (8 valence electrons), and has 15 protons, which is more than sodium (11 protons) but fewer than argon (18 protons).

If an atom of iodine gains one electron, it will have a total of 8 valence electrons, similar to the noble gas xenon. This is because iodine has 7 valence electrons in its neutral state, and gaining one electron allows it to achieve a full outer shell, characteristic of stable noble gases.

An element with 1 proton and 0 electrons is a hydrogen ion, specifically the hydrogen cation (H⁺). In its neutral state, hydrogen has one proton and one electron, but when it loses its electron, it becomes positively charged. This ion plays a crucial role in various chemical reactions, particularly in acid-base chemistry.

Atoms in a system move more rapidly as the energy increases, primarily due to the increase in thermal energy. At higher energy levels, atoms vibrate, rotate, and translate more vigorously, leading to increased kinetic energy. Conversely, at lower energy levels, atomic motion slows down, resulting in reduced kinetic energy and tighter bonding in solids. This relationship between energy and atomic movement is fundamental in understanding states of matter and phase transitions.

Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding and interactions. They determine an atom's reactivity and the types of bonds it can form with other atoms, as these electrons are involved in the formation of covalent or ionic bonds. The number of valence electrons influences whether an atom will gain, lose, or share electrons, ultimately shaping the molecule's properties and behavior. Thus, the arrangement and number of valence electrons directly dictate how an atom interacts with others.

An atom can increase in neutrons through a process called neutron capture, where it absorbs a neutron from its environment, often occurring in nuclear reactions or during radioactive decay. In certain nuclear reactions, such as those in stars or during supernova events, atoms can also gain neutrons as a byproduct of fusion or fission processes. Additionally, artificial methods, like those used in nuclear reactors, can facilitate the addition of neutrons to specific isotopes.

Atoms that have the same number of protons but a different number of neutrons are called isotopes. For example, carbon has two stable isotopes: carbon-12, which has 6 protons and 6 neutrons, and carbon-14, which has 6 protons and 8 neutrons. Both isotopes are forms of carbon, but their differing neutron counts result in different atomic masses and some variations in their nuclear stability and properties.

An electron falls back to a lower energy level when it loses energy, typically by emitting a photon. This process occurs when the electron transitions from a higher energy state to a lower one, which often happens after being excited to a higher energy level due to the absorption of energy. The emitted photon corresponds to the energy difference between the two levels, and its wavelength can be used to identify the specific transition.

Sulfur-25 has a total of 25 nucleons, which include both protons and neutrons. Sulfur has an atomic number of 16, meaning it has 16 protons. To find the number of neutrons, subtract the number of protons from the total nucleons: 25 - 16 = 9. Therefore, sulfur-25 has 9 neutrons.

If you have one proton and no neutrons in your nucleus, you are hydrogen-1, which is the most common isotope of hydrogen. In this case, the single proton serves as the nucleus, and the absence of neutrons makes it the simplest and lightest element in the periodic table.

One inaccurate statement about protons is that they have a negative charge; in reality, protons possess a positive charge. Additionally, claiming that protons are found outside the nucleus of an atom is incorrect, as they are located within the nucleus alongside neutrons. Finally, stating that protons have a negligible mass compared to electrons is misleading; protons are significantly more massive than electrons.

An oxide ion (O²⁻) has a charge of negative 2, meaning it has gained two extra electrons compared to its neutral state. A neutral oxygen atom has 8 protons, which is the atomic number of oxygen. Therefore, the oxide ion still has 8 protons, regardless of its charge.