The Periodic Table and Its History

An element is a simple substance that cannot be broken into anything simpler.

He discovered potassium by passing electricity through a compound of potassium.

A triad is a group of three elements with similar chemical properties in which the atomic weight of the middle element is approximately equal to the average of the other two.

<p>The properties of elements seemed to repeat with every eighth element.</p> Signup and view all the answers

<p>He arranged elements by increasing atomic weight and grouped them by similar properties, leading to the formulation of his Periodic Law.</p> Signup and view all the answers

<p>It led scientists to seek patterns to better organize and memorize the elements.</p> Signup and view all the answers

<p>It indicated that elements could be organized in a systematic way, reflecting their chemical behavior.</p> Signup and view all the answers

<p>The main goal was to find a structured way to classify and remember the growing list of discovered elements.</p> Signup and view all the answers

<p>Mendeleev's periodic law states that when elements are arranged in order of increasing atomic weight, their properties recur periodically.</p> Signup and view all the answers

<p>Mendeleev left gaps in his periodic table for elements that had not yet been discovered, predicting their properties.</p> Signup and view all the answers

<p>Mosely discovered that the atomic number is the number of protons in the nucleus and that elements can be arranged by increasing atomic number without having to reverse their order.</p> Signup and view all the answers

<p>The modern periodic table is arranged by increasing atomic number and contains no gaps for undiscovered elements.</p> Signup and view all the answers

<p>The mass number of sodium is 23, calculated as the sum of its 11 protons and 12 neutrons.</p> Signup and view all the answers

<p>The atomic number is the number of protons in the nucleus of an atom, denoted by the letter 'Z'.</p> Signup and view all the answers

<p>The number of neutrons can be calculated using the formula: Mass number (A) - Atomic number (Z).</p> Signup and view all the answers

<p>The modern periodic law states that when elements are arranged in order of increasing atomic number, their properties recur periodically.</p> Signup and view all the answers

<p>They move in curved paths and are separated according to their masses.</p> Signup and view all the answers

<p>Positive ions hit a detector, which amplifies the signal into an electric current displayed on a computer.</p> Signup and view all the answers

<p>K = 2, 8, 8, 1.</p> Signup and view all the answers

<p>The first energy level can hold 2 electrons.</p> Signup and view all the answers

<p>Electrons occupy the lowest available energy levels when building the electron configuration of an atom in its ground state.</p> Signup and view all the answers

<p>Ca = 1s2, 2s2, 2p6, 3s2, 3p6, 4s2.</p> Signup and view all the answers

<p>The 4s sublevel is lower in energy than the 3d sublevel.</p> Signup and view all the answers

<p>A d sublevel can hold a maximum of 10 electrons.</p> Signup and view all the answers

<p>Cr has the electron configuration 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5 because it achieves stability with half-filled d orbitals.</p> Signup and view all the answers

<p>Cu has the electron configuration 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10, indicating a fully filled 3d subshell for added stability.</p> Signup and view all the answers

<p>Al3+ has the electron configuration 1s2, 2s2, 2p6, which is the same as neon.</p> Signup and view all the answers

<p>S2- has the electron configuration 1s2, 2s2, 2p6, 3s2, 3p6, which is the same as Argon.</p> Signup and view all the answers

<p>Hund’s rule states that electrons will fill degenerate orbitals singly before pairing. For example, nitrogen has three electrons in the 2p sublevel filling px, py, and pz singly.</p> Signup and view all the answers

<p>The Pauli Exclusion Principle states that no more than two electrons can occupy an orbital and they must have opposite spins.</p> Signup and view all the answers

<p>The periodic system implies that when elements are arranged by increasing atomic weight, their properties recur periodically.</p> Signup and view all the answers

<p>Half-filled and fully filled sublevels are more stable due to lower energy states and increased electron repulsion minimization.</p> Signup and view all the answers

<p>Isotopes are atoms of the same element with the same atomic number but different mass numbers due to varying numbers of neutrons in the nucleus.</p> Signup and view all the answers

<p>The average mass of an atom of chlorine is 35.5.</p> Signup and view all the answers

<p>Francis William Aston built the mass spectrometer to measure the masses of atoms, leading to the discovery of isotopes.</p> Signup and view all the answers

<p>The primary principle of mass spectrometry is that charged particles are deflected to different extents in a magnetic field based on their masses.</p> Signup and view all the answers

<p>In ionization, atoms and molecules are converted into ions using an electron gun that knocks electrons off the sample, producing positive ions.</p> Signup and view all the answers

<p>Vaporization involves injecting a small amount of gas or liquid into the sample inlet, turning it into gas for analysis under vacuum conditions.</p> Signup and view all the answers

<p>Measuring relative abundances of isotopes is significant for accurately determining the average atomic mass of elements.</p> Signup and view all the answers

<p>Mass spectrometers can identify unknown compounds and detect banned drugs in athletes.</p> Signup and view all the answers

<p>Mendeleev placed iodine after tellurium to align it with other elements having similar chemical properties, such as chlorine and bromine.</p> Signup and view all the answers

<p>Noble gases were not included in the 1869 table because they had not been discovered yet.</p> Signup and view all the answers

<p>Atomic number is the number of protons in the nucleus of an atom, while relative atomic mass is the weighted average mass of an element's isotopes based on their natural abundance.</p> Signup and view all the answers

<p>Arranging elements by atomic number eliminates the need to reverse order to correctly group elements.</p> Signup and view all the answers

<p>An atomic energy level represents the fixed amount of energy that an electron can have in an atom.</p> Signup and view all the answers

<p>An orbit does not account for wave properties and the uncertainty principle, whereas an orbital incorporates both wave properties and the uncertainty principle.</p> Signup and view all the answers

<p>The emission spectrum of elements provides evidence for the existence of atomic energy levels.</p> Signup and view all the answers

<p>The electron configuration for a zinc atom is 1s2 2s2 2p6 3s2 3p6 3d10 4s2.</p> Signup and view all the answers