The Periodic Table.pdf

The Periodic Table 5.1 – 5.4  Agenda ✔ Describe the structure of an atom ✔ Learn about the methods and discoveries of Rutherford. ✔ Contributions of other scientist. ✔ Compare the first 20 elements of the periodic table in terms of their structure. ✔ Describe...

The Periodic Table 5.1 – 5.4  Agenda ✔ Describe the structure of an atom ✔ Learn about the methods and discoveries of Rutherford. ✔ Contributions of other scientist. ✔ Compare the first 20 elements of the periodic table in terms of their structure. ✔ Describe trends in some groups and periods of the periodic table.  Ernest Rutherford conducted a famous experiment in 1911 that led to a revolutionary understanding of the atom. He used alpha particles (positively charged particles) to bombard a thin gold foil. Rutherford's Rutherford's Experiment and Findings: Atomic Model Most alpha particles passed straight through the foil: This suggested that atoms are mostly empty space. A small number of alpha particles were deflected at large angles: This indicated the presence of a small, dense, positively charged core within the atom, which he called the nucleus. Rutherford's Atomic Model: Based on his experiment, Rutherford proposed the following atomic model: An atom has a tiny, dense, positively charged nucleus at its center. Most of the mass of the atom is concentrated in the nucleus. The negatively charged electrons orbit around the nucleus, much like planets orbiting the sun. The Building Blocks of Matter ; Atom Atoms are the incredibly tiny particles that make up everything around us. They are the basic building blocks of matter. Imagine them as the tiny bricks that construct everything from a grain of sand to a giant planet.  Structure of an Atom An atom consists of three main particles: 1. Protons: Positively charged particles found in the nucleus (center) of the atom. 2. Neutrons: Neutral particles (no charge) also found in the nucleus. 3. Electrons: Negatively charged particles that orbit around the nucleus. Electronic Representation of Elements Electronic configuration is a way of describing how electrons are distributed among the various atomic orbitals in an atom. It provides insights into an element's chemical properties and behavior.  A Map of Elements The; Periodic Table ⮚ A periodic table is like a map of all the known chemical elements. ⮚ Imagine the periodic table as a big family photo of all the What information does it provide? elements. ✔ Element symbol: A shorthand way to represent an ⮚ Each square on the table is like a family member with its element (e.g., H for hydrogen). own special traits. ✔ Atomic number: The number of protons in an atom of that element. ⮚ It's a way to organize them based on their properties. ✔ Atomic mass: The average mass of an atom of that How is it organized? element ✔ Rows: Called periods, elements in the same row have the same number of electron shells. ✔ Columns: Called groups, elements in the same column have similar chemical properties. ARRANGEMENT OF THE PERIODIC TABLE Trends in the Periodic Table ⮚ Periodic trends are change or development in a general direction of elements on the periodic table. ⮚ Major trends are ✔ electronegativity, ✔ ionization energy, ✔ electron affinity, ✔ atomic radius, ✔ metallic character. Trends in Group 1 (Alkali Metals) · Group 1 elements, also known as alkali metals, exhibit distinct trends as we move down the group from lithium (Li) to francium (Fr) · Elements in the same group (column) of the periodic table share similar chemical properties. · This is because they have the same number of electrons in their outermost energy level, called valence electrons. · Atomic radius increases: Atoms become larger due to the addition of The increase in atomic radius and the electron shells. decrease in ionization energy and electronegativity are due to the shielding · Ionization energy decreases: It becomes easier to remove an electron effect of inner electrons. from the outer shell as the distance from the nucleus increases. As more electron shells are added, the outer electron is shielded from the nuclear attraction, · Electronegativity decreases: The ability to attract electrons decreases as making it easier to remove. the outer electron is further from the nucleus. The increased reactivity is due to the ease · Metallic character increases: Elements become more metallic in their with which alkali metals lose their single properties. valence electron to form stable ions. · Reactivity increases: The elements become more reactive with water and other substances. · Melting and boiling points decrease: The metallic bonds weaken as atomic size increases. Trends in Reactivity  Trends in Periods of the Periodic Table ⮚ Elements within the same period (horizontal row) show distinct trends in their properties. ⮚ This is due to the consistent number of electron shells but increasing nuclear charge as we move across the period. ⮚ Trends in Periods: ✔ Atomic Radius: Decreases as you move across a period. This is because the increasing nuclear charge pulls the electrons closer to the nucleus. ✔ Ionization Energy: Increases as you move across a period. It becomes harder to remove an electron as the nuclear pull on the electrons increases. ✔ Electronegativity: Increases as you move across a period. Atoms become more attracted to electrons as they approach a full outer electron shell. ✔ Metallic Character: Decreases as you move across a period. Elements become less metallic and more non- metallic in their properties.  Period 2 · It consists of the elements lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne). · General trends across Period 2 from left to right: ⮚ Atomic radius decreases: The atoms become ⮚ The period shows a transition from metallic (Li, Be) to smaller as the nuclear charge increases, non-metallic (B to Ne) elements. pulling the electrons closer. ⮚ Carbon shows unique properties due to its ability to ⮚ Ionization energy increases: It becomes increasingly difficult to remove an electron form strong covalent bonds. as the nuclear charge increases. ⮚ Nitrogen, oxygen, and fluorine are highly reactive non- ⮚ Electronegativity increases: The tendency metals. of an atom to attract electrons increases as the nuclear charge grows. ⮚ Neon is a noble gas, unreactive due to its full outer ⮚ Metallic character decreases: Elements electron shell. become less metallic and more non-metallic ⮚ Understanding these trends helps explain the chemical and physical properties of Period 2 elements.