Chemistry: Early Discoveries and Theories
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Questions and Answers

Greek philosophers believed that the universe was made up of four main elements – Earth, Air, Wind and, ______.

Fire

Robert Boyle provided the first accurate definition of an ______ in his book 'The Sceptical Chemist'.

element

Humphry Davy discovered ______ by passing electricity through a compound of potassium.

potassium

By 1800, approximately ______ elements had been discovered.

<p>35</p> Signup and view all the answers

Johann Dobereiner noticed that bromine had properties that were halfway between ______ and iodine.

<p>chlorine</p> Signup and view all the answers

John Newland's Law of ______ states that elements' properties repeat every eight elements.

<p>Octaves</p> Signup and view all the answers

Dmitri Mendeleev arranged elements in order of increasing atomic ______.

<p>weight</p> Signup and view all the answers

Mendeleev called his findings the ‘______ Law’ due to the periodic reoccurrence of properties.

<p>Periodic</p> Signup and view all the answers

A fine beam of ______ passes into the analyser unit.

<p>ions</p> Signup and view all the answers

Positive ions are made to move in ______ paths using a magnetic field.

<p>curved</p> Signup and view all the answers

The signal from the detector is amplified into an electric ______.

<p>current</p> Signup and view all the answers

Potassium has 19 ______ and therefore, 19 electrons.

<p>protons</p> Signup and view all the answers

Energy level 1 (n=1) can only hold ______ electrons.

<p>two</p> Signup and view all the answers

Mendeleev’s Periodic law states that when elements are arranged in order of increasing atomic weight, their properties recur ______.

<p>periodically</p> Signup and view all the answers

Henry Mosely determined that the number of protons in the nucleus of an atom defines its ______.

<p>atomic number</p> Signup and view all the answers

According to the Aufbau Principle, electrons occupy the lowest available ______ levels.

<p>energy</p> Signup and view all the answers

In the modern periodic table, elements are arranged in order of increasing ______.

<p>atomic number</p> Signup and view all the answers

Calcium is element number 20 and contains 20 ______.

<p>electrons</p> Signup and view all the answers

The d sublevel can hold ______ electrons.

<p>10</p> Signup and view all the answers

The mass number of an element is the sum of the number of protons and ______.

<p>neutrons</p> Signup and view all the answers

The letter ‘Z’ is used to denote the ______ number of an element.

<p>atomic</p> Signup and view all the answers

Sodium has 11 protons and 12 neutrons, making its mass number ______.

<p>23</p> Signup and view all the answers

Mendeleev left ______ in his periodic table for elements that had not yet been discovered.

<p>gaps</p> Signup and view all the answers

The modern periodic law describes how properties of elements recur periodically when arranged by increasing ______.

<p>atomic number</p> Signup and view all the answers

Iodine has a lower relative atomic mass than ______.

<p>tellurium</p> Signup and view all the answers

The 1869 periodic table did not include any noble ______.

<p>gases</p> Signup and view all the answers

Isotopes are atoms of the same element, with the same atomic number, which have different mass numbers due to the different number of ______ in the nucleus.

<p>neutrons</p> Signup and view all the answers

Modern periodic tables arrange elements in order of ______.

<p>atomic number</p> Signup and view all the answers

The average mass of an atom of chlorine is ______.

<p>35.5</p> Signup and view all the answers

An atomic energy level refers to the fixed amount of ______ of an electron.

<p>energy</p> Signup and view all the answers

Francis William Aston built an instrument called a ______ to measure the masses of atoms.

<p>mass spectrometer</p> Signup and view all the answers

The evidence that supports the existence of atomic energy levels is the ______ spectrum.

<p>emission</p> Signup and view all the answers

A mass spectrometer is used to separate and identify ______, measure their relative abundances, and identify unknown compounds.

<p>isotopes</p> Signup and view all the answers

The electron configuration for a nickel atom in its ground state is ______.

<p>1s2 2s2 2px2 2py2 2pz2 3s2 3px2 3py2 3pz2 4s2 3d8</p> Signup and view all the answers

The principle of mass spectrometry is that charged particles moving in a ______ are deflected to different extents according to their masses.

<p>magnetic field</p> Signup and view all the answers

Relative atomic mass is expressed on a scale where carbon-12 has a mass of exactly ______ units.

<p>12</p> Signup and view all the answers

The ______ describes how an electron can exhibit both particle-like and wave-like behavior.

<p>orbital</p> Signup and view all the answers

In the first step of mass spectrometry, a small amount of gas or liquid is injected into the sample inlet and ______ occurs.

<p>vaporisation</p> Signup and view all the answers

Atoms and molecules are turned into ions using an electron gun in an ______ chamber.

<p>ionisation</p> Signup and view all the answers

During ______, positive ions pass through negatively charged plates, accelerating the ions to high speeds.

<p>acceleration</p> Signup and view all the answers

Chromium (Cr) has 24 electrons and is written as: Cr = 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d______

<p>5</p> Signup and view all the answers

Copper (Cu) has 29 electrons and is written as: Cu = 1s2, 2s2, 2p6, 3s2, 3p6, 4s______, 3d10

<p>1</p> Signup and view all the answers

An atom that has gained electrons becomes ______ charged.

<p>negatively</p> Signup and view all the answers

Aluminum is element number 13 and the Al3+ ion has a total of ______ electrons.

<p>10</p> Signup and view all the answers

The electronic configuration of the S2- ion is 1s2, 2s2, 2p6, 3s2, 3p______.

<p>6</p> Signup and view all the answers

Hund's rule of Maximum Multiplicity states that when two or more orbitals of equal energy are available, the electrons occupy them ______ before filling them in pairs.

<p>singly</p> Signup and view all the answers

The Pauli Exclusion Principle states that no more than ______ electrons may occupy an orbital.

<p>two</p> Signup and view all the answers

According to Mendeleev's periodic table, when elements are arranged in order of increasing atomic weight, their properties recur ______.

<p>periodically</p> Signup and view all the answers

Flashcards

Element (Definition)

A substance that cannot be split into simpler substances by chemical means.

Dobereiner's Triads

Groups of three elements with similar chemical properties; the middle element's atomic weight is about the average of the other two.

Newland's Law of Octaves

Arrangement of elements in which the 8th element (counting from a particular element) has properties similar to the first.

Mendeleev's Periodic Law

Arrangement of elements based on increasing atomic weight; elements with similar properties appear in vertical columns.

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Atomic Weight

A measure of the mass of an atom.

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Periodic Table

Arranged table of all known elements, organized by increasing atomic number or weight and recurring properties.

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Robert Boyle

Irish chemist who defined an element as a substance that can't be broken down by chemical means.

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Humphry Davy

English chemist who discovered several elements using electricity.

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Atomic Number

The number of protons in an atom's nucleus.

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Modern Periodic Table

An arrangement of elements ordered by increasing atomic number.

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Modern Periodic Law

The properties of elements recur periodically when arranged by increasing atomic number.

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Mass Number

The sum of protons and neutrons in an atom's nucleus.

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Atomic Number Symbol

The symbol used to denote the atomic number

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Mass Number Symbol

The symbol used to denote the mass number.

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Calculating Neutrons

Subtracting the atomic number from the mass number gives you the number of neutrons.

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Isotopes

Atoms of the same element with the same atomic number, but different mass numbers due to varying neutron counts in the nucleus.

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Average Atomic Mass

The weighted average of the masses of all naturally occurring isotopes of an element, taking their abundances into account. The reference standard is carbon-12 isotope, with a mass of exactly 12 units.

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Mass Spectrometer

A device used to separate and identify isotopes, measure their abundances, and determine the relative atomic mass of an element.

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Vaporisation in Mass Spectrometry

The process of converting a sample into a gas phase by applying a vacuum inside the spectrometer.

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Ionisation in Mass Spectrometry

The process of converting atoms or molecules into charged ions by firing electrons at the sample to knock off electrons.

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Acceleration in Mass Spectrometry

The process of speeding up the ions through negatively charged plates, increasing their kinetic energy.

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Deflection in Mass Spectrometry

Charged particles moving in a magnetic field are deflected to varying extents based on their masses.

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Mass Spectrometry Applications

Mass spectrometry has applications in various fields including identifying isotopes, determining unknown compounds, measuring relative atomic masses, and detecting banned substances.

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What is Hund's Rule?

When two or more orbitals of equal energy are available, electrons fill them singly before pairing up in the same orbital.

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What is the Pauli Exclusion Principle?

No more than two electrons can occupy an orbital, and they must have opposite spins.

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What is a neutral atom?

An atom that has an equal number of protons and electrons, resulting in a neutral charge.

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What is an ion?

An atom that has gained or lost electrons, resulting in a net positive or negative charge.

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What is a cation?

A positively charged ion formed when an atom loses electrons.

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What is an anion?

A negatively charged ion formed when an atom gains electrons.

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Electron configuration of Al3+?

Al3+ has 10 electrons: 1s2, 2s2, 2p6. It has the same electronic configuration as Neon.

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Electron configuration of S2-?

S2- has 18 electrons: 1s2, 2s2, 2p6, 3s2, 3p6. This is the same as Argon.

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Mass Spectrum

A visual representation of the different ions produced by a mass spectrometer. It shows the relative abundance of each ion based on its mass-to-charge ratio (m/z).

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Aufbau Principle

Electrons fill the lowest energy levels available first - like building up an atom, starting with the lowest floors.

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Electron Configuration (s,p)

The arrangement of electrons in the s and p sublevels of an atom's energy levels, using numbers to indicate the number of electrons in each sublevel.

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d-Block Elements

Elements in the periodic table where the d sublevel is being filled. These elements often have complex electron configurations due to the lower energy of the 4s level compared to the 3d level.

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Sublevel

A division within an energy level, where electrons have similar energies. The sublevels are designated as s, p, d, and f.

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Orbital

A region of space around the nucleus of an atom where an electron is most likely to be found.

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Energy Level

A region around the nucleus where electrons have a specific energy level. They are numbered 1, 2, 3, etc., with higher numbers corresponding to higher energies.

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Tellurium vs. Iodine

Tellurium (Te) and Iodine (I) were positioned incorrectly in Mendeleev's table because iodine has a lower atomic mass but similar chemical properties to chlorine and bromine. To maintain the group trends, Mendeleev switched their positions, prioritizing chemical similarities over atomic mass.

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Why no Noble Gases in Mendeleev's table?

Noble gases, such as helium and neon, were not included in Mendeleev's 1869 periodic table because they had not yet been discovered. Their unique properties and inert nature were unknown at the time.

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Modern Periodic Table - Atomic Number

The modern periodic table organizes elements in order of increasing atomic number, the number of protons in an atom's nucleus. This ensures elements with similar chemical properties fall into the same vertical columns (groups).

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What is Relative Atomic Mass?

Relative atomic mass is the average mass of an element's isotopes as they occur naturally, taking their abundances into account. It's measured relative to carbon-12, which has a mass of exactly 12 units.

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Advantage of Atomic Number Order

Arranging elements by atomic number eliminates the need to reverse the order of elements to fit them into their correct groups based on chemical properties. It simplifies the organization and avoids inconsistencies.

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What is an Atomic Energy Level?

An atomic energy level represents the fixed amount of energy an electron can possess within an atom. Electrons occupy specific energy levels, and they can only jump between these levels by absorbing or releasing energy.

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Orbit vs. Orbital

Bohr's atomic orbit is a circular path an electron travels around the nucleus. This model has limitations as it doesn't account for the wave nature of electrons or the uncertainty principle. An atomic orbital, however, is a probability distribution describing the likelihood of finding an electron in a specific region of space.

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Electron Configuration of Nickel

The electron configuration of nickel in its ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸. This indicates the distribution of electrons in various energy levels and sublevels within the atom.

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Study Notes

Greek Philosophers

  • Believed the universe was made of four elements: Earth, Air, Water, and Fire.

Robert Boyle

  • First accurately defined an element.
  • Described an element as a simple substance that cannot be broken down into simpler substances by chemical means.
  • Definition: An element is a substance that cannot be split into simpler substances by chemical means.

Humphrey Davy

  • Discovered potassium by passing electricity through a potassium compound.
  • Also discovered sodium, calcium, barium, strontium, and magnesium using the same method.

Dobereiner's Triads

  • Noticed patterns in the properties of elements.
  • Definition: 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.

Newlands' Octaves

  • Arranged known elements in order of atomic weights.
  • Noticed that the properties of elements seemed to repeat every eighth element.
  • Definition: Newland's octaves are arrangements of elements in which the first and eighth element (counting from a particular element) have similar properties.

Mendeleev

  • Arranged elements in order of increasing atomic weight.
  • Arranged similar elements in columns.
  • Noticed periodic reoccurrence of properties.
  • Definition: Mendeleev's Periodic law – When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the elements recur periodically.
  • Predicted properties of undiscovered elements.
  • Left gaps for undiscovered elements.
  • Re-ordered elements to fit into groups of similar properties.

Moseley's Atomic Number

  • Studied frequencies of X-rays emitted by atoms.
  • Determined the number of protons in an atom's nucleus.
  • Definition: The atomic number is the number of protons in the nucleus of that atom.
  • Arranged elements in order of increasing atomic number.
  • Modern periodic law - When elements are arranged in order of increasing atomic number, the properties of the elements recur periodically.

Modern Periodic Table

  • Elements are arranged in order of increasing atomic number.
  • Transition elements have their own block.
  • No gaps.

Atomic Numbers and Mass Numbers

  • Definition: The mass number of an element is the sum of the number of protons and neutrons in the nucleus of the atom of that element.
  • Letter 'Z' is used to denote the atomic number while the letter 'A' is used to denote the mass number.

Isotopes

  • Definition: Isotopes are atoms of the same element, with the same atomic number, which have different mass numbers due to the different number of neutrons in the nucleus.
  • Average mass of isotopes considered, taking into account abundance.

Mass Spectrometer

  • Used to measure the masses of atoms.
  • Used to identify isotopes.

Writing Electron Configurations

  • Electrons fill orbitals following rules.
  • Lowest energy levels always filled first.
  • Maximum number of electrons per orbital.
  • Configurations of ions.

Atomic Energy Levels

  • Fixed amount of energy of an electron in an atom.

Electronic Orbit and Orbitals

  • Orbit—Inconsistent with the wave properties of an electron and the uncertainty principle.
  • Orbital—Electron can have wave properties and the uncertainty principle is taken into account.

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The Periodic Table PDF

Description

Explore the fundamental concepts and discoveries of early chemists and philosophers. This quiz covers the beliefs of Greek philosophers, Robert Boyle's definition of elements, Humphrey Davy's discoveries through electrolysis, Dobereiner's triads, and Newlands' octaves. Test your knowledge of the foundational theories that shaped modern chemistry.

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