TABEL PERIODIK
Tabel Periodik Unsur Merupakan referensi kimia Susunan unsur-unsur dengan informasi dasar
• Dmitri Mendeleev, 1869: pengaturan unsur-unsur yang diketahui dalam bentuk tabel periodik, sebelum ada detail struktur atom. – – – –
Berdasar: sifak fisik dan kimia unsur Sifat kimia unsur meningkat secara periodik Digolongkan berdasar massa atom Prediksi unknown elements: ada posisi kosong bila unsurnya tidak sesuai dgn yg diatas dan dibawah
– Saat unknown elements ditemukan, sifat-sifatnya mendekati yg diprediksi.
Tabel periodik: penyusunan unsur-unsur yang mana unsur-unsur tersebut dipisahkan menjadi grup-grup berdasarkan set pengulangan sifat-sifatnya. -disusun berdasar kenaikan nomor atom -terdiri dari deretan (periode) dan kolom (grup) unsur-unsur
⇒ mempermudah dalam membandingkan sifat unsur yg satu dengan yang lainnya.
Periodisitas • Hukum berkala: sifat-sifat kimia dan fisika unsur-unsur merupakan fungsi berkala dari nomor atomnya. • Periodisitas kimia tidak berhubungan dengan massa atom, namun berhubungan dgn jumlah protonnya. • Perilaku kimiawi unsur ditentukan oleh konfigurasi elektronnya • Tingkatan energi terkuantisasi sesuai lapisan elektron disekitar inti. • Tiap deretan (periode) diawali dgn kulit elektron terluar yang baru. – ditandai dengan kulit (n) sama ⇒ 1 deretan dlm sistem periodik • Kolom dalam sistem periodik: grup, mengandung unsur-unsur yg memiliki sifat kimia dan fisik yg serupa. – diidentifikasi dari jumlah elektronnya pada kulit terluar, kecuali He
• Menampilkan informasi: • Nomor atom • Simbol • Massa atom • Jumlah elektron valensi • Wujud zat pd suhu kamar
1
Sifat Logam • Logam: unsur-unsur yg umumnya padatan pada suhu kamar. Paling banyak diantaranya adalah logam. • Non-logam: unsur-unsur pada pojok kanan atas tabel periodik. • Metalloid: unsur-unsur yang berada pada batas diagonal antara logam dan non-logam. Sifat kimiafisiknya merupakan intermediet logam dan nonlogam.
Detail sifat2.
Alkali Metals
Alkaline Earth Metals
• The alkali family is found in the first column of the periodic table. • Atoms of the alkali metals have a single electron in their outermost level, in other words, 1 valence electron. • They are shiny, have the consistency of clay, and are easily cut with a knife.
• They are never found uncombined in nature. • They have two valence electrons. • Alkaline earth metals include magnesium and calcium, among others. • They are the most reactive metals. • They react violently with water. • They are always bonded with another element.
Transition Metals • Transition Elements include those elements in the B families. • These are the metals you are probably most familiar: copper, tin, zinc, iron, nickel, gold, and silver. • They are good conductors of heat and electricity. • The compounds of transition metals are usually brightly colored and are often used to color paints. • Transition elements have 1 or 2 valence electrons, which they lose when they form bonds with other atoms. Some transition elements can lose electrons in their next-tooutermost level. • Transition elements have properties similar to one another and to other metals, but their properties do not fit in with those of any other family. • Many transition metals combine chemically with oxygen to form compounds called oxides.
Boron Family • The Boron Family is named after the first element in the family. • Atoms in this family have 3 valence electrons. • This family includes a metalloid (boron), and the rest are metals. • This family includes the most abundant metal in the earth’s crust (aluminum).
2
Carbon Family • Atoms of this family have 4 valence electrons. • This family includes a nonmetal (carbon), metalloids, and metals. • The element carbon is called the “basis of life.” There is an entire branch of chemistry devoted to carbon compounds called organic chemistry.
Oxygen Family • Atoms of this family have 6 valence electrons. • Most elements in this family share electrons when forming compounds. • Oxygen is the most abundant element in the earth’s crust. It is extremely active and combines with almost all elements.
Noble Gases
Nitrogen Family • The nitrogen family is named after the element that makes up 78% of our atmosphere. • This family includes nonmetals, metalloids, and metals. • Atoms in the nitrogen family have 5 valence electrons. They tend to share electrons when they bond. • Other elements in this family are phosphorus, arsenic, antimony, and bismuth.
Halogen Family • The elements in this family are fluorine, chlorine, bromine, iodine, and astatine. • Halogens have 7 valence electrons, which explains why they are the most active non-metals. They are never found free in nature.
Halogen atoms only need to gain 1 electron to fill their outermost energy level. They react with alkali metals to form salts.
Rare Earth Elements • The thirty rare earth elements are composed of the lanthanide and actinide series.
• Noble Gases are colorless gases that are extremely un-reactive. • One important property of the noble gases is their inactivity. They are inactive because their outermost energy level is full. • Because they do not readily combine with other elements to form compounds, the noble gases are called inert. • All have complete octets: stability. • The family of noble gases includes helium, neon, argon, krypton, xenon, and radon. • All the noble gases are found in small amounts in the earth's atmosphere.
• One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.
3
Ionic Radii
Atomic Radii Properties
The ionic radius of each ion is the portion of the distance between the nuclei occupied by that ion Cations are smaller than the atoms from which they are formed - the nucleus attracts the remaining electrons more strongly Anions are larger than the atoms from which they are formed - the greater number of electrons repel more strongly
Ionization Energy Ionization energy is the energy required to remove an electron from a ground state atom in the gaseous state
Electron Affinity Electron affinity is the energy change that occurs when an electron is added to a gaseous atom
Electron affinities are expressed as negative because the process is exothermic
A Summary of Periodic Trends
R I N G K A S A N
• Jumlah elektron valensi – Meningkat dalam 1 periode (kiri ke kanan) – Sama jika dalam satu gol.
• Ukuran atom – Menurun dalam 1 periode – Meningkat dalam 1 gol. (atas ke bawah)
• Energi ionisasi – Meningkat dalam 1 periode – Menurun dalam 1 gol.
• Afinitas elektron – Meningkat dalam 1 periode – Menurun dalam 1 gol.
• Elektronegativitas – Meningkat dalam 1 periode – Menurun dalam 1 gol.
• Ukuran ion – Menurun dalam 1 periode – Meningkat dalam 1 gol.
• Sifat logam – Menurun dalam 1 periode – Meningkat dalam 1 gol.
4
ATOMIC STRUCTURE
He
2 4
ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells
Atomic number the number of protons in an atom
Atomic mass the number of protons and neutrons in an atom
number of electrons = number of protons
around the nucleus of an atom. •
first shell
a maximum of 2 electrons
•
second shell
a maximum of 8 electrons
•
third shell
a maximum of 8 electrons
ELECTRONIC CONFIGURATION
ATOMIC STRUCTURE There are two ways to represent the atomic structure of
With electronic configuration elements are represented
an element or compound;
numerically by the number of electrons in their shells and number of shells. For example;
1. 2.
Electronic Configuration Dot & Cross Diagrams
Nitrogen 2 in 1st shell 5 in 2nd shell
configuration = 2 , 5
2
+
N
5 = 7
7
14
ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; 20
a)
Ca
b)
Na
Cl
17
e) 35
c)
O
Si
f)
B
14 28
8
16
23
40
d)
11
5 11
5
