mount - How to access unallocated internal HDD on Ubuntu 16.04?

I recently did a fresh install of 16.04 on the solid state drive, leaving a 1.8 TB unallocated partition on the internal HDD.

Somehow I can't access this partition on /dev/sda/ and also can't mount it:

sudo mount /dev/sda /media/sda/

mount: wrong fs type, bad option, bad superblock on /dev/sda,
       missing codepage or helper program, or other error

sudo fdisk -l

Disk /dev/nvme0n1: 477 GiB, 512110190592 bytes, 1000215216 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: A9243158-8BFD-4A7F-BF8B-E9F415F4573D

Device             Start        End   Sectors   Size Type
/dev/nvme0n1p1      2048    1050623   1048576   512M EFI System
/dev/nvme0n1p2   1050624  966858751 965808128 460.5G Linux filesystem
/dev/nvme0n1p3 966858752 1000214527  33355776  15.9G Linux swap



Disk /dev/sda: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 50BEB1BE-9E9E-4F9A-8F7C-E3A7BA81A788

Gparted shows /dev/sda/ as unallocated space.

Do I have to perform some type of disk repair? Or should I just allocate that space using Gparted?

You can't mount an empty disk, but only filesystems. Therefore you have to create a partition (/dev/sda1) on /dev/sda, make a filesystem in the partition and mount the partition /dev/sda1.

So use gparted to create a partition /dev/sda1, possibly covering the complete disk /dev/sda. Then sudo mkfs -t ext4 /dev/sda1 and sudo mount /dev/sda1 .