Problem 1 - Chemistry A Guided Inquiry

Question

For each of the following neutral atoms give the core charge. a) Li. b) \(\quad \ddot{\mathrm{Cl}}\) c) He:

Step-by-Step Solution

Answer

The core charges for Li, Cl, and He are +3, +17, and +2 respectively.

Step 1: Determine the Atomic Number for Li

Looking at the periodic table, Li or Lithium has an atomic number of 3. Therefore, the core charge of a Lithium atom is +3.

Step 2: Determine the Atomic Number for Cl

Still referring to the periodic table, Cl or Chlorine has an atomic number of 17. Thus, the core charge for a Chlorine atom is +17.

Step 3: Determine the Atomic Number for He

Finally, He or Helium on the periodic table displays an atomic number of 2. This indicates that the core charge of a Helium atom is +2.

Key Concepts

Atomic Number

The atomic number is a fundamental property of an element and indicates the number of protons in the nucleus of an atom. It uniquely identifies an element on the periodic table. For example, if we consider the element Lithium, it is represented by the symbol Li and has an atomic number of 3. This number tells us that every neutral atom of Lithium contains exactly three protons.

It's important for students to understand that the atomic number is always a whole number and does not change for a given element. It's also directly connected to the core charge of an atom. The core charge gives us an idea about the strength of the charge within the nucleus, which is determined by the total number of protons, thus it is equal to the atomic number. For neutral atoms, which have equal numbers of protons and electrons, the core charge can be thought of as the 'effective nuclear charge' that an electron experiences.

Periodic Table

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. Elements are presented in order of increasing atomic number, which is displayed with its own box and contains key information about the elements.

The periodic table is structured in rows referred to as periods and columns known as groups. Elements within the same group typically have similar properties due to their analogous electron configurations. Understanding the layout of the periodic table is vital for grasping core charge, as it allows you to quickly identify the atomic number of an element. For instance, Chlorine (Cl) falls in period 3 and group 17, and is assigned an atomic number of 17. By understanding the periodic table, students can recognize patterns and predict the properties of elements, including their core charges, which are pivotal for understanding chemical reactivity and bonding.

Neutral Atoms

Neutral atoms are atoms where the number of protons (positively charged particles) equals the number of electrons (negatively charged particles). The overall electrical charge of a neutral atom is zero because the positive and negative charges balance out. For example, Helium (He) is a neutral atom with an atomic number of 2. This means it has two protons and, when neutral, also has two electrons.

Knowing that an atom is neutral simplifies finding the core charge. In neutral atoms, the core charge corresponds directly to the number of protons since it is not 'cancelled out' by an equal number of electrons. So, the core charge of Helium will be +2, indicative of its two protons. Grasping this concept helps students to further understand chemical bonding and reactions, as the balance between protons and electrons plays a crucial role in the stability and reactivity of an atom.