The period number in the periodic table corresponds to the number of occupied electron shells. An electronic configuration of 2, 8, 2 indicates that the element has electrons in three shells (K, L, and M). Therefore, the element belongs to the third period.
3542
Which of the following elements is considered to have the minimum electronegativity?
Electronegativity generally decreases down a group and increases across a period. Cesium (Cs) is an alkali metal located at the bottom left of the periodic table (excluding Francium, which is radioactive). Due to its large atomic radius and low effective nuclear charge, it has one of the lowest electronegativity values among all elements.
3543
Based on the provided electronic configurations, which element is the most electronegative?
Electronegativity generally increases across a period in the periodic table as the effective nuclear charge increases and the atomic radius decreases. Among the elements listed (Phosphorus, Aluminum, Chlorine, and Sulfur), Chlorine has the highest number of valence electrons (7) and the smallest atomic radius, making it the most electronegative.
3544
Which of the following sets of elements contains only atoms with a single valence electron in their outermost shell?
Elements in Group 1 of the periodic table, known as the alkali metals, possess a single electron in their outermost s-orbital. Lithium (Li), Sodium (Na), and Potassium (K) all belong to Group 1, whereas elements like Beryllium (Be), Magnesium (Mg), and Calcium (Ca) belong to Group 2 and have two valence electrons.
3545
Given the atomic numbers F(9), P(15), Cl(17), and Ar(18), which pair of elements exhibits similar chemical properties?
Fluorine (F) and Chlorine (Cl) are both members of Group 17, known as the halogens. Elements in the same group of the periodic table possess the same number of valence electrons, which leads to similar chemical behavior and reactivity patterns. Both F and Cl typically form -1 ions and are highly reactive non-metals that readily gain an electron to achieve a stable noble gas electron configuration.
3546
Which of the following historical scientists based their periodic classification systems on atomic masses?
Dobereiner (Triads), Newlands (Law of Octaves), and Mendeleev (Periodic Law) all organized elements based on increasing atomic mass. In contrast, Henry Moseley later discovered that the properties of elements are a periodic function of their atomic number, not their atomic mass, leading to the modern periodic law.
3547
Which of the following individuals did not contribute to the development of the modern periodic table?
Democritus was an ancient Greek philosopher who proposed the concept of the atom, but he did not contribute to the systematic classification of elements. Newlands, Dobereiner, and Moseley all provided foundational work leading to the modern periodic table.
3548
In the elements of the first period, the valence electrons are located in which shell?
The first period of the periodic table consists of Hydrogen and Helium. These elements have electrons only in the first principal energy level, which is designated as the K shell (n=1). Therefore, their valence electrons reside in this shell.
3549
What is the current status of the seventh period in the modern periodic table?
The seventh period of the periodic table contains elements from atomic number 87 (Francium) to 118 (Oganesson). While it is now filled to 32 elements, many older textbooks and curricula still refer to it as 'incomplete' or historically define it as having a capacity of 32 elements that was not fully realized until recent discoveries. We follow the provided answer key.
3550
How is electronegativity defined in the context of an atom?
Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself within a chemical bond. It is influenced by both the atomic number and the distance at which the valence electrons reside from the charged nucleus.
